literature search assignment

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How to undertake a literature search: a step-by-step guide

Affiliation.

• 1 Literature Search Specialist, Library and Archive Service, Royal College of Nursing, London.
• PMID: 32279549
• DOI: 10.12968/bjon.2020.29.7.431

Undertaking a literature search can be a daunting prospect. Breaking the exercise down into smaller steps will make the process more manageable. This article suggests 10 steps that will help readers complete this task, from identifying key concepts to choosing databases for the search and saving the results and search strategy. It discusses each of the steps in a little more detail, with examples and suggestions on where to get help. This structured approach will help readers obtain a more focused set of results and, ultimately, save time and effort.

Keywords: Databases; Literature review; Literature search; Reference management software; Research questions; Search strategy.

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• Step 3: Conduct Literature Searches

Systematic Reviews: Step 3: Conduct Literature Searches

Created by health science librarians.

• Step 1: Complete Pre-Review Tasks
• Step 2: Develop a Protocol

About Step 3: Conduct Literature Searches

Partner with a librarian, systematic searching process, choose a few databases, search with controlled vocabulary and keywords, acknowledge outdated or offensive terminology, helpful tip - building your search, use nesting, boolean operators, and field tags, build your search, translate to other databases and other searching methods, document the search, updating your review.

• Searching FAQs
• Step 4: Manage Citations
• Step 5: Screen Citations
• Step 6: Assess Quality of Included Studies
• Step 7: Extract Data from Included Studies
• Step 8: Write the Review

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In Step 3, you will design a search strategy to find all of the articles related to your research question. You will:

• Define the main concepts of your topic
• Choose which databases you want to search
• List terms to describe each concept
• Add terms from controlled vocabulary like MeSH
• Use field tags to tell the database where to search for terms
• Combine terms and concepts with Boolean operators AND and OR
• Translate your search strategy to match the format standards for each database
• Save a copy of your search strategy and details about your search

There are many factors to think about when building a strong search strategy for systematic reviews. Librarians are available to provide support with this step of the process.

Click an item below to see how it applies to Step 3: Conduct Literature Searches.

Reporting your review with PRISMA

For PRISMA, there are specific items you will want to report from your search.  For this step, review the PRISMA-S checklist.

• PRISMA-S for Searching
• Specify all databases, registers, websites, organizations, reference lists, and other sources searched or consulted to identify studies. Specify the date when each source was last searched or consulted. Present the full search strategies for all databases, registers and websites, including any filters and limits used.
• For information on how to document database searches and other search methods on your PRISMA flow diagram, visit our FAQs "How do I document database searches on my PRISMA flow diagram?" and "How do I document a grey literature search for my PRISMA flow diagram?"

Managing your review with Covidence

For this step of the review, in Covidence you can:

• Document searches in Covidence review settings so all team members can view
• Add keywords from your search to be highlighted in green or red while your team screens articles in your review settings

How a librarian can help with Step 3

When designing and conducting literature searches, a librarian can advise you on :

• How to create a search strategy with Boolean operators, database-specific syntax, subject headings, and appropriate keywords 
• How to apply previously published systematic review search strategies to your current search
• How to test your search strategy's performance 
• How to translate a search strategy from one database's preferred structure to another

The goal of a systematic retrieve is to find all results that are relevant to your topic. Because systematic review searches can be quite extensive and retrieve large numbers of results, an important aspect of systematic searching is limiting the number of irrelevant results that need to be screened. Librarians are experts trained in literature searching and systematic review methodology. Ask us a question or partner with a librarian to save time and improve the quality of your review. Our comparison chart detailing two tiers of partnership provides more information on how librarians can collaborate with and contribute to systematic review teams.

Search Process

• Use controlled vocabulary, if applicable
• Include synonyms/keyword terms
• Choose databases, websites, and/or registries to search
• Translate to other databases
• Search using other methods (e.g. hand searching)
• Validate and peer review the search

Databases can be multidisciplinary or subject specific. Choose the best databases for your research question. Databases index various journals, so in order to be comprehensive, it is important to search multiple databases when conducting a systematic review. Consider searching databases with more diverse or global coverage (i.e., Global Index Medicus) when appropriate. A list of frequently used databases is provided below. You can access UNC Libraries' full listing of databases on the HSL website (arranged alphabetically or by subject ).

Generally speaking, when literature searching, you are not searching the full-text article. Instead, you are searching certain citation data fields, like title, abstract, keyword, controlled vocabulary terms, and more. When developing a literature search, a good place to start is to identify searchable concepts of the research question, and then expand by adding other terms to describe those concepts. Read below for more information and examples on how to develop a literature search, as well as find tips and tricks for developing more comprehensive searches.

Identify search concepts and terms for each

Start by identifying the main concepts of your research question. If unsure, try using a question framework to help identify the main searchable concepts. PICO is one example of a question framework and is used specifically for clinical questions. If your research question doesn't fit into the PICO model well, view other examples of question frameworks and try another!

View our example in PICO format

Question: for patients 65 years and older, does an influenza vaccine reduce the future risk of pneumonia.

Controlled Vocabulary

Controlled vocabulary is a set of terminology assigned to citations to describe the content of each reference. Searching with controlled vocabulary can improve the relevancy of search results. Many databases assign controlled vocabulary terms to citations, but their naming schema is often specific to each database. For example, the controlled vocabulary system searchable via PubMed is MeSH, or Medical Subject Headings. More information on searching MeSH can be found on the HSL PubMed Ten Tips Legacy Guide .

Note: Controlled vocabulary may be outdated, and some databases allow users to submit requests to update terminology.

View Controlled Vocabulary for our example PICO

As mentioned above, databases with controlled vocabulary often use their own unique system. A listing of controlled vocabulary systems by database is shown below.

Keyword Terms

Not all citations are indexed with controlled vocabulary terms, however, so it is important to combine controlled vocabulary searches with keyword, or text word, searches. 

Authors often write about the same topic in varied ways and it is important to add these terms to your search in order to capture most of the literature. For example, consider these elements when developing a list of keyword terms for each concept:

• American versus British spelling
• hyphenated terms
• quality of life
• satisfaction
• vaccination
• influenza vaccination

There are several resources to consider when searching for synonyms. Scan the results of preliminary searches to identify additional terms. Look for synonyms, word variations, and other possibilities in Wikipedia, other encyclopedias or dictionaries, and databases. For example, PubChem lists additional drug names and chemical compounds.

Display Controlled Vocabulary and Keywords for our example PICO

Combining controlled vocabulary and text words in PubMed would look like this:

"Influenza Vaccines"[Mesh] OR "influenza vaccine" OR "influenza vaccines" OR "flu vaccine" OR "flu vaccines" OR "flu shot" OR "flu shots" OR "influenza virus vaccine" OR "influenza virus vaccines"

Social and cultural norms have been rapidly changing around the world. This has led to changes in the vocabulary used, such as when describing people or populations. Library and research terminology changes more slowly, and therefore can be considered outdated, unacceptable, or overly clinical for use in conversation or writing.

For our example with people 65 years and older, APA Style Guidelines recommend that researchers use terms like “older adults” and “older persons” and forgo terms like “senior citizens” and “elderly” that connote stereotypes. While these are current recommendations, researchers will recognize that terms like “elderly” have previously been used in the literature. Therefore, removing these terms from the search strategy may result in missed relevant articles. 

Research teams need to discuss current and outdated terminology and decide which terms to include in the search to be as comprehensive as possible. The research team or a librarian can search for currently preferred terms in glossaries, dictionaries, published guidelines, and governmental or organizational websites. The University of Michigan Library provides suggested wording to use in the methods section when antiquated, non-standard, exclusionary, or potentially offensive terms are included in the search.

Check the methods sections or supplementary materials of published systematic reviews for search strategies to see what terminology they used. This can help inform your search strategy by using MeSH terms or keywords you may not have thought of. However, be aware that search strategies will differ in their comprehensiveness.

You can also run a preliminary search for your topic, sort the results by Relevance or Best Match, and skim through titles and abstracts to identify terminology from relevant articles that you should include in your search strategy.

Nesting is a term that describes organizing search terms inside parentheses. This is important because, just like their function in math, commands inside a set of parentheses occur first. Parentheses let the database know in which order terms should be combined. 

Always combine terms for a single concept inside a parentheses set. For example: 

( "Influenza Vaccines"[Mesh] OR "influenza vaccine" OR "influenza vaccines" OR "flu vaccine" OR "flu vaccines" OR "flu shot" OR "flu shots" OR "influenza virus vaccine" OR "influenza virus vaccines" )

Additionally, you may nest a subset of terms for a concept inside a larger parentheses set, as seen below. Pay careful attention to the number of parenthesis sets and ensure they are matched, meaning for every open parentheses you also have a closed one.

( "Influenza Vaccines"[Mesh] OR "influenza vaccine" OR "influenza vaccines" OR "flu vaccine" OR "flu vaccines" OR "flu shot" OR "flu shots" OR "influenza virus vaccine" OR "influenza virus vaccines" OR   (( flu OR influenza ) AND ( vaccine OR vaccines OR vaccination OR immunization )))

Boolean operators

Boolean operators are used to combine terms in literature searches. Searches are typically organized using the Boolean operators OR or AND. OR is used to combine search terms for the same concept (i.e., influenza vaccine). AND is used to combine different concepts (i.e., influenza vaccine AND older adults AND pneumonia). An example of how Boolean operators can affect search retrieval is shown below. Using AND to combine the three concepts will only retrieve results where all are present. Using OR to combine the concepts will retrieve results that use all separately or together. It is important to note that, generally speaking, when you are performing a literature search you are only searching the title, abstract, keywords and other citation data. You are not searching the full-text of the articles.

The last major element to consider when building systematic literature searches are field tags. Field tags tell the database exactly where to search. For example, you can use a field tag to tell a database to search for a term in just the title, the title and abstract, and more. Just like with controlled vocabulary, field tag commands are different for every database.

If you do not manually apply field tags to your search, most databases will automatically search in a set of citation data points. Databases may also overwrite your search with algorithms if you do not apply field tags. For systematic review searching, best practice is to apply field tags to each term for reproducibility.

For example:

("Influenza Vaccines"[Mesh] OR "influenza vaccine"[tw] OR "influenza vaccines"[tw] OR "flu vaccine"[tw] OR "flu vaccines"[tw] OR "flu shot"[tw] OR "flu shots"[tw] OR "influenza virus vaccine"[tw] OR "influenza virus vaccines"[tw] OR ((flu[tw] OR influenza[tw]) AND (vaccine[tw] OR vaccines[tw] OR vaccination[tw] OR immunization[tw])))

View field tags for several health databases

For more information about how to use a variety of databases, check out our guides on searching.

• Searching PubMed guide Guide to searching Medline via the PubMed database
• Searching Embase guide Guide to searching Embase via embase.com
• Searching Scopus guide Guide to searching Scopus via scopus.com
• Searching EBSCO Databases guide Guide to searching CINAHL, PsycInfo, Global Health, & other databases via EBSCO

Combining search elements together

Organizational structure of literature searches is very important. Specifically, how terms are grouped (or nested) and combined with Boolean operators will drastically impact search results. These commands tell databases exactly how to combine terms together, and if done incorrectly or inefficiently, search results returned may be too broad or irrelevant.

For example, in PubMed:

(influenza OR flu) AND vaccine is a properly combined search and it produces around 50,000 results.

influenza OR flu AND vaccine is not properly combined.  Databases may read it as everything about influenza OR everything about (flu AND vaccine), which would produce more results than needed.

We recommend one or more of the following:

• put all your synonyms together inside a set of parentheses, then put AND between the closing parenthesis of one set and the opening parenthesis of the next set
• use a separate search box for each set of synonyms
• run each set of synonyms as a separate search, and then combine all your searches
• ask a librarian if your search produces too many or too few results

View the proper way to combine MeSH terms and Keywords for our example PICO

Question: for patients 65 years and older, does an influenza vaccine reduce the future risk of pneumonia .

Translating search strategies to other databases

Databases often use their own set of terminology and syntax. When searching multiple databases, you need to adjust the search slightly to retrieve comparable results. Our sections on Controlled Vocabulary and Field Tags have information on how to build searches in different databases.  Resources to help with this process are listed below.

• Polyglot search A tool to translate a PubMed or Ovid search to other databases
• Search Translation Resources (Cornell) A listing of resources for search translation from Cornell University
• Advanced Searching Techniques (King's College London) A collection of advanced searching techniques from King's College London

Other searching methods

Hand searching.

Literature searches can be supplemented by hand searching. One of the most popular ways this is done with systematic reviews is by searching the reference list and citing articles of studies included in the review. Another method is manually browsing key journals in your field to make sure no relevant articles were missed. Other sources that may be considered for hand searching include: clinical trial registries, white papers and other reports, pharmaceutical or other corporate reports, conference proceedings, theses and dissertations, or professional association guidelines.

Searching grey literature

Grey literature typically refers to literature not published in a traditional manner and often not retrievable through large databases and other popular resources. Grey literature should be searched for inclusion in systematic reviews in order to reduce bias and increase thoroughness. There are several databases specific to grey literature that can be searched.

• Open Grey Grey literature for Europe
• OAIster A union catalog of millions of records representing open access resources from collections worldwide
• Grey Matters: a practical tool for searching health-related grey literature (CADTH) From CADTH, the Canadian Agency for Drugs and Technologies in Health, Grey Matters is a practical tool for searching health-related grey literature. The MS Word document covers a grey literature checklist, including national and international health technology assessment (HTA) web sites, drug and device regulatory agencies, clinical trial registries, health economics resources, Canadian health prevalence or incidence databases, and drug formulary web sites.
• Duke Medical Center Library: Searching for Grey Literature A good online compilation of resources by the Duke Medical Center Library.

Systematic review quality is highly dependent on the literature search(es) used to identify studies. To follow best practices for reporting search strategies, as well as increase reproducibility and transparency, document various elements of the literature search for your review. To make this process more clear, a statement and checklist for reporting literature searches has been developed and and can be found below.

• PRISMA-S: Reporting Literature Searches in Systematic Reviews
• Section 4.5 Cochrane Handbook - Documenting and reporting the search process

At a minimum, document and report certain elements, such as databases searched, including name (i.e., Scopus) and platform (i.e. Elsevier), websites, registries, and grey literature searched. In addition, this also may include citation searching and reaching out to experts in the field. Search strategies used in each database or source should be documented, along with any filters or limits, and dates searched. If a search has been updated or was built upon previous work, that should be noted as well. It is also helpful to document which search terms have been tested and decisions made for term inclusion or exclusion by the team. Last, any peer review process should be stated as well as the total number of records identified from each source and how deduplication was handled. 

If you have a librarian on your team who is creating and running the searches, they will handle the search documentation.

You can document search strategies in word processing software you are familiar with like Microsoft Word or Excel, or Google Docs or Sheets. A template, and separate example file, is provided below for convenience. 

• Search Strategy Documentation Template
• Search Strategy Documentation Example

*Some databases like PubMed are being continually updated with new technology and algorithms. This means that searches may retrieve different results than when originally run, even with the same filters, date limits, etc.

When you decide to update a systematic review search, there are two ways of identifying new articles:  

1. rerun the original search strategy without any changes. .

Rerun the original search strategy without making any changes.  Import the results into your citation manager, and remove all articles duplicated from the original set of search results.

2. Rerun the original search strategy and add an entry date filter.

Rerun the original search strategy and add a date filter for when the article was added to the database ( not the publication date).  An entry date filter will find any articles added to the results since you last ran the search, unlike a publication date filter, which would only find more recent articles.

Some examples of entry date filters for articles entered since December 31, 2021 are:

• PubMed:   AND ("2021/12/31"[EDAT] : "3000"[EDAT])
• Embase: AND [31-12-2021]/sd
• CINAHL:   AND EM 20211231-20231231
• PsycInfo: AND RD 20211231-20231231
• Scopus:   AND LOAD-DATE AFT 20211231  

Your PRISMA flow diagram

For more information about updating the PRISMA flow diagram for your systematic review, see the information on filling out a PRISMA flow diagram for review updates on the Step 8: Write the Review page of the guide.

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Learning Objectives

(1) Explain steps in conducting a literature search

(2) Identify resources to utilize in a literature search

(3) Perform an online literature search using U of U Health resources

Valentina is a third year pediatric resident who notices that many of the teenagers she sees in clinic use their phones to play games and connect with friends and family members. She wonders if there could be an app for teenagers to manage their chronic diseases, specifically type 1 diabetes. But where does she begin? 

What is a literature search?

iterature search is a comprehensive exploration of published literature with the purpose of finding scholarly articles on a specific topic . Managing and organizing selected scholarly works can also be useful.

Why do a literature search?

Literature search is a critical component for any evidence-based project. It helps you to understand the complexity of a clinical issue, gives you insight into the scope of a problem, and provides you with best treatment approaches and the best available evidence on the topic. Without this step, your evidence-based practice project cannot move forward.

Five steps for literature search success

There are several steps involved in conducting a literature search. You may discover more along the way, but these steps will provide a good foundation. 

Plan using PICO(T) to develop your clinical question and formulate a search strategy.

Identify a database to search.

Conduct your search in one or more databases.

Select relevant articles .

Organize your results . Remember that searching the literature is a process.

#1: Plan using PICO(T)

The PICO(T) question framework is a formula for developing answerable, researchable questions. Using PICO(T) guides you in your search for evidence and may even help you be more efficient in the process ( Click here to learn all about PICO(T) ). 

Once you have your PICO(T) question you can formulate a search strategy by identifying key words, synonyms and subject headings. These can help you determine which databases to use. 

#2: Identify a database

For your search, you will need to consult a variety of resources to find information on your topic. While some of these resources will overlap, each also contains unique information that you won’t find in other databases.  

The "Big 3" databases: Embase, PubMed, and Scopus are always important to search because they contain large numbers of citations and have a fairly broad scope. ( Click here to access these databases and others in the library's A to Z database.) 

In addition to searching these expansive databases, try one that is more topic specific.

We are here to help.

If you are conducting a literature search and are not certain of the details, don't panic! U of U Health has a wealth of resources, including experienced librarians, to help you through the process. Learn more here. 

Utah’s Epic-embedded librarian support

Did you know you can request evidence-based information from the library directly through Epic?  Contact us through Epic’s Message Basket.

Eccles Health Sciences medical librarians are able to provide expertise in articulating the clinical question, identifying appropriate data sources, and locating the best evidence in the shortest amount of time. You can also send a message to ASK EHSL .

#3: Conduct your search

Now that you have identified pertinent databases, it is time to begin the search!

Use the key words that you’ve identified from your PICO(T) question to start searching. You might start your search broadly, with just a few key words, and then add more once you see the scope of the literature. If the initial search doesn't produce many results, you can play with removing some key words and adding more granular detail.

In our intro case study, Valentina’s population is teenagers with type 1 diabetes and her intervention is a mobile app. Watch the video below to see how Valentina uses the powerful Embase PICO search feature to identify synonyms for type 1 diabetes, mobile apps, and teenagers.

Example of   Embase using PICO Why use Embase? This search casts a wider net than most databases for more results.

Common Search Terms and Symbols

AND Includes both keywords Narrows search OR Either keyword/concept Combine synonyms and similar concepts Expands search "Double quotes"  Specific phrase Wildcard* Any word ending variants (singular, plural, etc.) Example: nurs* = nurse, nurses, nursing, etc.

Controlled Vocabulary

Want to help make your search more accurate? Try using the controlled vocabulary, or main words or phrases that describe the main themes in an article, within databases. Controlled vocabulary is a standardized hierarchical system. For example, PubMed uses Medical Subject Headings or MeSH terms to “map” keywords to the controlled vocabulary. Not all databases use a controlled vocabulary, but many do. Embase’s controlled vocabulary is called Emtree, and CINAHL’s  controlled vocabulary is called CINAHL Headings. Consider focusing the controlled vocabulary as the major topic when using MeSH, Emtree, or CINAHL Headings. 

For Valentina’s question, there are MeSH terms for Adolescent, Diabetes Mellitus, Type 1, and Mobile Applications.

Example of  PubMed using MeSH MeSH helps focus your PubMed search

Talk with your librarians for more help with searching with controlled vocabularies. 

Every database uses filters to help you narrow your search. There are different filters in each database, but they tend to work in similar ways. Use filters to help you refine your search, rather than adding those keywords to the search. Filters include article/publication type, age, language, publication years, and species.

Using filters can help return the most accurate results for your search.

Article/publication types, such as randomized controlled trial, systematic reviews, can be used as filters.

Use an Age Filter, rather than adding “pediatric” or “geriatric” to your search.

Valentina uses the age filter for her question rather than as a keyword in the video below.

Example of a PubMed keyword search using filters PubMed is the most common search because it is the most widely available.

#4: Select relevant articles

Once you have completed your search, you’ll select articles that are relevant to your question. Some databases also include a “similar articles” feature which recommends other articles similar to the article you’re reviewing—this can also be a helpful tool.

When you’ve identified an article that appears relevant to your topic, use the “Snowballing” technique to find additional articles. Snowballing involves reviewing the reference lists of articles from your search. 

In other words, look at your key articles and review their reference list for additional key or seminal articles to aid in your search.

#5: Organize your results

As you begin to collect articles during your literature search, it is important to store them in an organized fashion. Most research databases include personalized accounts for storing selected references and search strategies. 

Reference managers are a great way to not only keep articles organized, but they also generate in-text citations and bibliographies when writing manuscripts, and provide a platform for sharing references with others working on your project.

A number of reference managers—such as Zotero , EndNote , RefWorks, Mendeley , and Papers are available. EndNote Basic (web-based) is freely available to U of U faculty, staff and students. If you need help with this process, contact a librarian to help you select the reference manager  that will best suit your needs.

Using these steps, you’re ready to start your literature search. It is important to remember that there is not a right or wrong way to do the search. Literature searches are an iterative process—it will take some time and negotiation to find what you are looking for. You can always change your approach, or the information resource you are using. The important thing is to just keep trying. And before you get frustrated or give up, contact a librarian . They are here to help!

This article originally appeared May 12, 2020. It was updated to reflect current practice on March 14, 2021.

Tallie Casucci

Barbara wilson.

You have a good idea about what you want to study, compare, understand or change. But where do you go from there? First, you need to be clear about exactly what it is you want to find out. In other words, what question are you attempting to answer? Librarian Tallie Casucci and nursing leaders Gigi Austria and Barb Wilson help us understand how to formulate searchable, answerable questions using the PICO(T) framework.

EBP, or evidence-based practice, is a term we encounter frequently in today’s health care environment. But what does it really mean for the health care provider? College of Nursing interim dean Barbara Wilson and Nurse manager Gigi Austria explain how to integrate EBP into all aspects of patient care.

Frequent and deliberate practice is critical to attaining procedural competency. Cheryl Yang, pediatric emergency medicine fellow, shares a framework for providing trainees with opportunities to learn, practice, and maintain procedural skills, while ensuring high standards for patient safety.

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Help and support.

• Finding information on your research topic
• How do I do a literature search?
• Accessibility statement: Library

A literature search is a systematic, thorough search of a range of literature (for example books, peer-reviewed articles, etc.) on your topic. Commonly you will be asked to undertake literature searches as part of your Level 3 and postgraduate study.

Literature searching can be broken down into a series of iterative steps. You may want to revisit some of these several times throughout your search.

Planning your search

What to search for: keywords and phrases.

Start the process by clarifying the research question you would like answered. Your next step is to use your research question to help you identify keywords. The language and terminology of your module materials will help you to identify the most effective words for your search.

You can also identify keywords by looking for background information on key areas within your topic online as this will give you ideas for synonyms and other words commonly used.

The activity on Choosing good keywords will provide further guidance.

Where to search: Library Search, databases and Google Scholar

Now that you have your keywords you need to decide where to search. Library Search is a good starting point, particularly for unfamiliar topics, to provide background information and lead to further sources.

Each database has different content. It is therefore advisable to search several databases to make sure you do not miss a key paper on your topic. If you are unsure where to search, the Selected resources for your study page will help you find the most relevant databases. 

You may also like to use Google Scholar too. The Access eresources using Google Scholar page shows how to add a "Find it at OU" button to Google Scholar search results.

Search techniques

Once you have your keywords you will need to combine them. You can use the help sheet on Advanced search techniques as guidance. You may also find the following activities useful:

The Library online training session on Smarter searching with library databases .

The activity on Filtering information quickly .

Further reading:

Byrne, D. (2017) Developing a researchable question . Project Planner . Sage Research Methods. DOI:10.4135/9781526408525.

Byrne, D. (2017) Reviewing the literature . Project Planner . Sage Research Methods. DOI:10.4135/9781526408518.

Evaluating information

It is important to evaluate the literature you find for quality and relevance. The PROMPT criteria will help with this. The longer Evaluating the quality of information activity provides more detail. (An OU login is required to access this activity.)

Organising information

When conducting a literature search recording the information you find in an organised manner is essential. Literature searches require you to read and keep track of many more articles than you would read for an assignment. You may want to try using a bibliographic management tool to help organise the references you have found. The Bibliographic management page introduces a selection of tools..

Keeping a record of the information you find could help you to save a lot of time. The Organising information activity introduces some methods to manage this material. (An OU login is required to access this activity.)

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Literature Reviews

What is a literature review.

• Literature Review Process

Purpose of a Literature Review

• Choosing a Type of Review
• Developing a Research Question
• Searching the Literature
• Searching Tips
• ChatGPT [beta]
• Documenting your Search
• Using Citation Managers
• Concept Mapping
• Writing the Review
• Further Resources

The Library's Subject Specialists are happy to help with your literature reviews!  Find your Subject Specialist here . 

If you have questions about this guide, contact Librarian  Jamie Niehof ([email protected]).

A literature review is an overview of the available research for a specific scientific topic. Literature reviews summarize existing research to answer a review question, provide context for new research, or identify important gaps in the existing body of literature.

An incredible amount of academic literature is published each year, by estimates over two million articles .

Sorting through and reviewing that literature can be complicated, so this Research Guide provides a structured approach to make the process more manageable.

THIS GUIDE IS AN OVERVIEW OF THE LITERATURE REVIEW PROCESS:

• Getting Started (asking a research question | defining scope)
• Organizing the Literature
• Writing the Literature Review (analyzing | synthesizing)

A  literature search  is a systematic search of the scholarly sources in a particular discipline. A  literature review   is the analysis, critical evaluation and synthesis of the results of that search. During this process you will move from a review  of  the literature to a review  for   your research.   Your synthesis of the literature is your unique contribution to research.

WHO IS THIS RESEARCH GUIDE FOR?

— those new to reviewing the literature

— those that need a refresher or a deeper understanding of writing literature reviews

You may need to do a literature review as a part of a course assignment, a capstone project, a master's thesis, a dissertation, or as part of a journal article. No matter the context, a literature review is an essential part of the research process. 

WHAT IS THE PURPOSE OF A LITERATURE REVIEW?

A literature review is typically performed for a specific reason. Even when assigned as an assignment, the goal of the literature review will be one or more of the following:

• To communicate a project's novelty by identifying a research gap

• An overview of research issues , methodologies or results relevant to field
• To explore the  volume and types of available studies
• To establish familiarity with current research before carrying out a new project
• To resolve conflicts amongst contradictory previous studies

Reviewing the literature helps you understand a research topic and develop your own perspective.

A LITERATURE REVIEW IS NOT :

• An annotated bibliography – which is a list of annotated citations to books, articles and documents that includes a brief description and evaluation for each entry
• A literary review – which is a critical discussion of the merits and weaknesses of a literary work
• A book review – which is a critical discussion of the merits and weaknesses of a particular book
• Next: Choosing a Type of Review >>
• Last Updated: May 9, 2024 11:44 AM
• URL: https://guides.lib.umich.edu/litreview

Searching the Literature

About literature searching.

• Select a Topic
• Search the Literature
• Evaluate & Select Sources
• Write & Cite Sources

What is a literature search?

Searching the literature is a key part of the research process. This is how scholars—and students—find out more about a topic. 

A literature search is the first step in sharing an overview on a topic. Common types of overviews include: annotated bibliography, systematic review, and literature review.

What do I need to do for my search?

You should review your assignment requirements to determine if you need to create a specific type of literature review.

When you do a literature search, you may look at sources such as:

• journal articles
• grey literature (like government publications, working papers, and policy statements)

You will probably have to do literature searches throughout your coursework.

Interested in reading more about literature searches?

Review these readings from Sage Research Methods to learn more:

• Project Planner: Reviewing the Literature (from Sage Research Methods) Learn how to: explain what a literature review is and why you need to do one, define the steps in a literature search and a literature review, get an overview of where to look for appropriate literature more... less... This section takes you through the literature review process, explaining the reasons for reviewing the literature and differentiation between the types of literature available.
• << Previous: Home
• Next: Select a Topic >>
• Last Updated: Feb 1, 2024 2:10 PM
• URL: https://libguides.sjf.edu/literature-search

Literature Searching

In this guide.

• Introduction
• Steps for searching the literature in PubMed
• Step 1 - Formulate a search question
• Step 2- Identify primary concepts and gather synonyms
• Step 3 - Locate subject headings (MeSH)
• Step 4 - Combine concepts using Boolean operators
• Step 5 - Refine search terms and search in PubMed
• Step 6 - Apply limits

Students and researchers in the health sciences are often required to conduct literature searches for a number of reasons including identifying appropriate studies and methods to include in a literature review manuscript. Understanding the basics of database searching can allow you to effectively and efficiently find the information you need. This guide takes you through the process of developing an advanced, robust literature search in PubMed . 

While the guide is based on searching in the PubMed database, the strategies can be applied appropriately to other databases, such as Embase , CINAHL , PsycINFO , etc. (see search syntax for more information on search translation). For more information on searching in other databases, attend Lane's Literature Reviews Beyond PubMed: Crafting Effective Searches in Other Databases  course.

If you're interested in conducting a systematic review, please visit Introduction to Systematic Reviews . 

Research Services

• Literature Searches
• Data Service
• Research Metrics Service
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Literature or reviews of a systematic nature is a value-added service available for current members of the Stanford Medicine community. To qualify for the service, the project lead and point-of-contact to Lane must be a Stanford affiliate.

Lane Medical Library staff can help you with your search strategy creation, collaborate on systematic reviews and other knowledge syntheses, provide guidance on documentation, processes, and tools, among others. Reviews or projects the team can help you with include but are not limited to:

• Systematic Review
• Meta-Analysis
• Literature Review for Grant Application
• Thesis or Dissertation
• Course Assignment
• Scoping Review
• Book Chapter
• Thesis Report

If you are interested in collaborating with a Lane Medical Librarian on a review project, please submit a  literature search request .

Data management and sharing is a component of Open Science, which aims to make scientific research more transparent and accessible. Proper data management and sharing benefit you as an individual and the research community as a whole. Lane's data service provides: 

• Best practices related to data management and sharing
• Assistance in complying with requirements related to the management and sharing of research data (e.g. from a publisher or funder)
• Consultations related to research data management, data security, data publishing, data curation, and long-term preservation
• Workshops and classes related to best practices in data management and sharing

For more information, visit the Data Management and Sharing guide .

Research metrics measure the impact of a scholar, article, book, journal, or research institution. Metrics can be informed through different approaches, such as citation counts, that can add to a broader understanding of impact. Lane's research metrics service assists with:

• Understanding, measuring and using bibliometrics and other statistical analysis of publications 
• Using alternative metrics (also known as altmetrics) 
• Common tools for assessing research impact

For more information on research metrics, visit the Research Impact guide.

Lane Librarians can help you with the authoring and publishing of your manuscript such as:

• Learn about unique author identifiers and how to create an ORCID ID
• How to find journals relevant to areas of research/interest for possible submission
• How to find journal impact factors
• Help find instructions for authors
• Explore alternate publishing models including open access journals
• How to verify citations

We also provide discounted Open Access author processing fees. For more information, visit our Understanding Open Access guide.  

• Next: Steps for searching the literature in PubMed >>
• Last Updated: Jul 10, 2024 2:17 PM
• URL: https://laneguides.stanford.edu/LitSearch

Searching the Literature: The Basics

• Getting Started
• Ask a Question
• Select a Search Resource
• Develop Search Terms
• Execute the Search
• Access/Save Results
• Evaluate & Improve Your Search
• Database Fundamentals This link opens in a new window
• Ovid Medline This link opens in a new window
• CINAHL This link opens in a new window
• Cochrane Library This link opens in a new window
• PubMed This link opens in a new window
• Web of Science This link opens in a new window
• Google Scholar This link opens in a new window
• Additional Resources

What is a Literature Search?

A literature search is the act of gathering existing knowledge or data around a topic or research question.  

Regardless of the purpose of your literature search, all searches follow the same basic process:

• Ask a question
• Select a search resource
• Develop search terms
• Execute the search
• Access results
• Evaluate & improve your search

Each page in this guide explores a different step of the process and lays the groundwork for the following steps.

Why Search the Literature?

E.g. "I want to learn more about treatment options available for quitting smoking."

E.g. "I need some statistics for how smoking rates have changed over the last 20 years."    

E.g. "I'm designing a research study on the effectiveness of hypnosis for smoking cessation.  What's been done before?  What areas need further investigation?"    

E.g. "I want to gather and synthesize all the existing studies that help answer the following research question: Are support groups more effective than nicotine-replacement products for helping teenagers quit smoking?"

E.g. "What treatment should I recommend to my teenage patient interested in quitting smoking?"

• Next: Ask a Question >>
• Last Updated: Aug 7, 2024 11:58 AM
• URL: https://hslmcmaster.libguides.com/literature_searching

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The RCN recommends using an updated browser such as Microsoft Edge or Google Chrome

How to undertake a literature search

Introduction.

Undertaking a literature search can be a daunting prospect. By breaking the exercise down into smaller steps, you can make the process more manageable. The following ten steps will help you complete the task from identifying key concepts to choosing databases for your search and saving your results and search strategy. It discusses each of the steps in a little more detail with examples and suggestions of where to get help.

There are ten steps to undertaking a literature search which we'll take you through below:

🎬 - Indicates a video is available with more information.

Please click on the boxes below to get a bit more detail on each step.

First, write out your title and check that you understand all the terms. Look up the meaning of any you don’t understand. An online dictionary or medical encyclopaedia may help with this.

If your search is for a dissertation, you may need to choose your own research question. In this case, you will need to consider whether there is likely to be enough research on your topic. Alternatively, if your topic is too broad, you could be overwhelmed by the number of references.

One way of checking how much is written on your topic is to use Library Search. Most libraries offer a Library Search or discovery tool. It provides a quick search across all the library’s holdings. You can also limit your search by date or type of document. If you just need a few references to help you write an essay, Library Search may be helpful. It also gives quick access to full text items.

Next, you need to identify your key concepts. One way to do this is to look at your title and identify the most important words. Ignore words that tell you what to do with the information you find eg evaluate, assess, compare, as these are not generally used as search terms. In the example below, key concepts have been highlighted:

Evaluate the effectiveness of a mindfulness intervention on the health-related quality of life of rheumatoid arthritis patients

Another way to do this is to break down your title using the PEO framework:

P = Population    E = Exposure    O = Outcome 

This works well where there is no comparison between two types of treatment or intervention.

In our example:

P = rheumatoid arthritis patients

E = mindfulness

O =  health related quality of life

Other question formats are available such as PICO or SPIDER

Tip: Not all search topics will include every element of PICO – some include fewer items.

Once you have identified the key concepts, it’s important to think of any other terms or phrases that might have a very similar meaning. Including such synonyms will make your search as thorough as possible. For example, if your topic is looking for articles on Staff attitudes , you might also use the terms:

• Staff perceptions 
• Staff opinions
• Stereotyping
• Labelling 

If the database you are using has a list of subject heading s , this may help you to find the most appropriate term for your subject. Some databases provide definitions for terms used in the database and may suggest related terms.

A comprehensive search will usually include both subject headings from databases and terms that you have thought of yourself.

Tip: Often your search term will be a phrase instead of a single word. To carry out phrase searches, use double quotes, for example “problem drinking”.

Once you have chosen your search terms, you need to think about the best databases for your topic. The databases you choose will depend on the search question and the libraries you have access to.

Tip: It’s well worth taking a few minutes to get to know the databases available on the Library webpages and what they cover.

The next step is to combine your search terms in such a way that you only retrieve the more relevant references for your search question. In order to do this you need to build a search strategy . This involves using Boolean operators such as AND , OR and NOT .

AND narrows the results of the search by ensuring that all the search terms are present in the results. 

OR broadens the results of the search by ensuring that any of the search terms are present in the results.

NOT limits the results by rejecting a particular search term. Be careful with NOT because it will exclude any results containing that search term regardless of whether other parts of the article might have been of interest.

OR will broaden your number of results while AND will produce fewer results.

Try using this  Search-plan-worksheet   to break your topic down into concepts. These can then be linked together when you run the search. You can also add synonyms within each concept box. The yellow limits box is a prompt to think about any limits you want to apply when searching. This leads us to Step 6.

Tip: Most databases will allow you to use a truncation sign (*) or wildcard (?) to pick up various different endings to words or alternative spellings.

For example:  alcohol* would pick up alcohol, alcoholic, alcoholism, etc

Sm?th would find Smith and Smyth

The next step is to think about any other restrictions you want to make to your results.

Common limiters found on databases include:

• Peer reviewed articles
• Research articles
• Age group (adult, child, older person)
• Document type

Not all databases allow all of the limiters above.

When writing a dissertation, primary research articles are normally required. Where the database allows you, try limiting to research articles only.

Non-research materials can also be useful as an overview of your topic; for example a literature review can give an analysis of what has already been written on a topic.

The video below includes a demonstration of how limits can be applied using the CINAHL database as an example:

CINAHL - advanced

Once you have identified all your search terms and any limits you want to apply, you are ready to run your search on the databases you have chosen. 

Once you have some search results, you can look through them and start to select those that look relevant to your literature search. It is likely you will reject some because they are not quite what you wanted but there will be others that can be marked for further attention.

The title of an article on its own may not tell you very much; read the abstract quite carefully to see if the article is relevant or not.

Tip: You can show more details for each record by clicking on the article title. On some databases, there may be an abstract for the article which you can open. 

If you find you are either generating more results than you can possibly look at or too few results to write about, be prepared to adjust your search terms and the way they are combined.

If you get too many results you could try: •limiting to just the most recent material •adding another term or concept and linking it using “AND” •limiting to a particular country or geographical area such as UK

If you get too few results, you might try: •expanding your date range •removing any geographical limits you have applied  •removing the least important term or concept

Tip: Be prepared to try other databases and keep searching until you feel confident you have found enough relevant material.

Once you have selected some articles that look relevant for your piece of work, you will need to save them so that your hard work is not wasted.

At the same time, you will want to save your search strategy . This is a record of the terms you searched, how you combined them, any limits you applied and how many results you found.

You will also need to choose a way to save your results. One way is to email the results to yourself and this can be done from all the databases .

Another way is to export your results to reference management software such as Zotero, RefWorks, EndNote or Mendeley. This software allows you to collect, organise and cite research. It is suitable for managing references over a long period of time. 

The RCN Library and Museum provides help with using Zotero . 

Tip: Keep a record of all the databases you use as you carry out your search. It is also a good idea to note where you found any references you subsequently use for your dissertation.

The final step is to obtain the full text of the articles identified in your search which you believe may be useful for your assignment. If you are lucky, many of these will be available electronically and you may just be able to follow a link to the full text.

Alternatively you can copy and paste your article title into the Library search box  and if it is available as full text, a hyperlink will be shown which will link you to the document.

If you are studying elsewhere and have access to a university or hospital library, they may subscribe to different journals to the RCN Library so it is worth exploring what they can offer. If your library does not have either an electronic copy or a physical copy, you may need to request the article by interlibrary loan .

Tip: It is also worth using Google or other browsers to check for the article title you require. Sometimes the article has been made freely available on the internet by the authors.

Boolean operators – words (AND, OR and NOT) which can be used to combine search terms in order to widen or limit the search results.

Database – this is an online collection of citations to journal articles which have been indexed to make retrieval easier. Some databases which also provide full text access to the articles.

Limits – these are options within a database which allow search results to be broken down further. Common limits are year(s) of publication, document type and language. MEDLINE and CINAHL allow age limits too.

Search Strategy – the list of search terms and limits used to retrieve relevant articles from a database in order to answer a search question.

Subject headings – terms that have been assigned to describe a concept that may have many alternative keywords. All these alternative keywords or terms are brought together under the umbrella of this single term. Most health-related databases use subject headings.

Additional information

If after following these steps, you still can’t find what you are looking for, remember that there is always help available at your library. The RCN Library and Museum offers a range of help materials via our Literature searching and training pages . These include: • Databases guides in electronic and printed formats • Video tutorials on how to search the databases • 1-1 training sessions pre-bookable via the RCN website face to face or via zoom

A reading list is also available on dissertation and essay support which provides suggestions for key resources, books and journal articles which may help. Click on the link below to access this list:

Dissertation and essay support reading list

Here are other resources you may also find helpful. You will find links to each resource below too:

• Aveyard H (2019) Doing a literature review in health and social care: a practical guide . 4th edn. London: Open University Press.
• Bettany-Satlikov J (2016) How to do a systematic literature review in nursing: a step-by-step guide . 2nd edn. Maidenhead: Open University Press.
• Coughlan M and Cronin P (2016) Doing a literature review in nursing, health and social care . 2nd edn. Los Angeles: Sage.
• De Brún C, Pearce-Smith N, Heneghan C, Perera R and Badenoch D (2014) Searching skills toolkit: finding the evidence . 2nd edn. Chichester: Wiley Blackwell / BMJ Books.
• Hewitt-Taylor J (2017) The essential guide to doing a health and social care literature review . London: Routledge. 

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What is a literature search?

A literature search is a systematic , thorough search of all types of literature relevant to a topic of interest. You may be required to undertake a literature review for exploration of a new topic, publication, or as part of your medical degree. Using a worked example , this article will outline the basic steps of a literature search and equip you with tips and tricks along the way!

Steps of a literature search

Step 1: define your research question.

The first step is to know exactly what question you want to answer . A common mistake is to attempt to conduct your literature search before you have a basic grasp of your topic area. Take some time to read articles about your topic to get a sense of how much information is available for a future literature review and to understand the language and terminology employed in that particular field. Equally, it is important to familiarise yourself with existing publications to ensure you do not duplicate efforts from existing work (better to find this out as early as you can)!

You should aim to find and read at least 3-5 articles in the topic area that you are investigating.

Once you have read a few articles, try and work out (hopefully with the help of a supervisor) the specific question you want to be answered.* It is useful to frame your question in PICO format :

• P opulation
• I ntervention
• C omparison

*Take your time here , and do not be afraid to talk to your supervisors or co-authors about the exact research question. Not having this clear at the outset will only complicate things further down the line.

I wanted to review the use of ketamine, an NMDA receptor antagonist, in the pre-hospital setting. I first performed an internet search of articles by typing in “ketamine pre-hospital”. I opened and skimmed the first 8-10 peer-reviewed publications from my search, and found the following:

• Ketamine can be indicated for either sedation or analgesia in the pre-hospital setting in the UK, Australia, USA and globally.
• Ketamine is often used in the A&E setting
• A review of the topic had been done in 2011

Upon further reflection and guidance from my supervisors, I decided to clarify my question as:

• “What is the effect of ketamine as an analgesic in the pre-hospital setting, compared with alternative analgesic regimens?”

Population : any patients requiring pre-hospital analgesia

Intervention : the administration of ketamine, with no restriction on the route of administration

Comparison : any analgesic regimen for the reduction of pre-hospital pain without the concurrent administration of ketamine

Outcome : the primary outcome was satisfactory pain relief. Secondary outcomes were the reported incidence and types of adverse effects and complications from the use of ketamine.

Step 2: How and where to search

Now that we have our research question and maybe a few articles that would be included in our search, it is time to create a search strategy .

Find keywords

First, review the articles (ones you have previously found/now found through a simple internet search) surrounding the topic and specifically, look at the keywords used in those articles. This will help you create your search string to input into the database.

In PubMed®, you may find keywords either at the bottom of the abstract or the bottom of the article (Figure 1). 2

Table of keywords

Next, create a table of keywords using the PICO format , and decide which columns are most appropriate to run in the search. Try and use all the potential synonyms that you think are appropriate (within reason). 

Table 1 . Table of keywords using PICO from publication 1

Database search

Now that you have your keywords, you need to identify databases to run your search in . Unfortunately, no singular database will include every article, therefore it is advisable to search a few to ensure that you do not miss any important ones. It is best to start with a broad database that is likely to include a significant number of papers. Potential starting points include:

Step 3: Running a search

Once you’ve identified an initial search engine, enter your keywords . The main functions that are relevant to searching include:

• “OR” : Use this when you are combining terms that may be synonyms to ensure you capture the concept you are looking for. Items in the same column (as per above) are generally combined with “or”
• “AND” : Use this to stratify different concepts . Items in different rows (as per above) are generally combined with “and”
• “Sort by year “: If you are only looking at articles from say 2000, you can sort by year to only include articles published beyond this point
• “ Sort by paper type” : Similar to the above, but for types of studies (e.g. RCT)

For example, it would be: “Ketamine” OR “Ketanest OR “Ketalar” AND “analgesia” OR “analgesic” OR “pain relief” OR “pain” OR “ pain management” AND “prehospital” OR “pre-hospital” OR “out of hospital” OR “out-of-hospital” OR “ambulance”

Once you have run the search, see how many articles come back to you and verify that it is a reasonable number . There is no exact science for this, but 15, 000 papers may mean that your question or search strategy is too broad. Conversely, a search strategy yielding ten papers may indicate your question is too narrow or your search strategy has missed a number of articles.

You can check against the papers that you have initially identified , to make sure they are included in your search. This may provide some reassurance that you have run the search correctly.

Step 4: Repeat search strategy across databases

Use the guidance of your supervisors to see if there are particular databases specific to your topic area that may be useful to perform an additional search in. Once you have identified others, apply the same principles above to search for articles there. Some additional databases include:

• Web of Science©
• EBM Reviews Complete

Step 5: Article inclusion and exclusion

Once you have a full list of potential articles (this list may be quite long), you will need to apply exclusion and inclusion criteria to ensure that you only select the articles that are relevant to your research question. This is normally done in two phases,  requiring two authors. These two phases will sequentially sieve your articles to leave only the ones that you need.

To begin, perform a title and/or abstract review of the papers . Read the title, and the abstract if necessary, of each paper to evaluate whether the article should be included in a future review. If you are unsure, keep the article in the included list for now.

At this point, you should also remove any and all duplicates . Although you may have 500-2000 articles, you will get into a rhythm with this, and hopefully, just from the title, you will be able to easily categorise a large number of your articles.

You should now have a significantly smaller list of articles in the included list . A full-text review should be performed on these. This involves reading the full text to further clarify whether or not an article should be included.

Step 6: Checking your work

A few fears are that either you will send your article list to your supervisor and they will get back to you saying that you’ve missed a few key articles , or even more frustratingly, you write a draft of your paper and then are told/find out about a key article that you have missed . Here are a few helpful tips to avoid this:

• Forward and backwards referencing the articles that you have found. 4  Forward referencing is looking at the articles that are cited by the paper that you are reading, as some of these may be relevant to your search. Backwards referencing is looking at what articles the paper you are reading has been cited in, as these may also be relevant.
• Consider looking for grey literature . Grey literature is research produced by organisations outside of traditional commercial or academic publishing channels. This can include private-sector reports, government documents, white papers and evaluation. Kings College London has a list of places you might find grey literature. 3
• Look at trial registers which provide access to information on public and privately conducted clinical trials in humans.

Step 7: Final list of articles

Now that you have a final list of articles, you are ready to extract relevant information from them into your review!

Future directions can include:

• Writing a systematic review
• Producing guidelines
• Drafting hospital protocols

Best of luck!

• Bansal, A., Miller, M., Ferguson, I., & Burns, B. Ketamine as a Prehospital Analgesic: A Systematic Review . Published in 2020. Available from: [LINK]
• Pubmed, National Library of Medicine. Available from: [LINK]
• Libguides Searching for Systematic Review: Grey Literature. Published in 2017. Available from: [LINK]
• Atkinson, L., & Cipriani, A. How to carry out a literature search for a systematic review: A practical guide . Published in 2018. Available from: [LINK]

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What is a literature review?

A literature review is an integrated analysis -- not just a summary-- of scholarly writings and other relevant evidence related directly to your research question.  That is, it represents a synthesis of the evidence that provides background information on your topic and shows a association between the evidence and your research question.

A literature review may be a stand alone work or the introduction to a larger research paper, depending on the assignment.  Rely heavily on the guidelines your instructor has given you.

Why is it important?

A literature review is important because it:

• Explains the background of research on a topic.
• Demonstrates why a topic is significant to a subject area.
• Discovers relationships between research studies/ideas.
• Identifies major themes, concepts, and researchers on a topic.
• Identifies critical gaps and points of disagreement.
• Discusses further research questions that logically come out of the previous studies.

APA7 Style resources

APA Style Blog - for those harder to find answers

1. Choose a topic. Define your research question.

Your literature review should be guided by your central research question.  The literature represents background and research developments related to a specific research question, interpreted and analyzed by you in a synthesized way.

• Make sure your research question is not too broad or too narrow.  Is it manageable?
• Begin writing down terms that are related to your question. These will be useful for searches later.
• If you have the opportunity, discuss your topic with your professor and your class mates.

2. Decide on the scope of your review

How many studies do you need to look at? How comprehensive should it be? How many years should it cover? 

• This may depend on your assignment.  How many sources does the assignment require?

3. Select the databases you will use to conduct your searches.

Make a list of the databases you will search. 

Where to find databases:

• use the tabs on this guide
• Find other databases in the Nursing Information Resources web page
• More on the Medical Library web page
• ... and more on the Yale University Library web page

4. Conduct your searches to find the evidence. Keep track of your searches.

• Use the key words in your question, as well as synonyms for those words, as terms in your search. Use the database tutorials for help.
• Save the searches in the databases. This saves time when you want to redo, or modify, the searches. It is also helpful to use as a guide is the searches are not finding any useful results.
• Review the abstracts of research studies carefully. This will save you time.
• Use the bibliographies and references of research studies you find to locate others.
• Check with your professor, or a subject expert in the field, if you are missing any key works in the field.
• Ask your librarian for help at any time.
• Use a citation manager, such as EndNote as the repository for your citations. See the EndNote tutorials for help.

Review the literature

Some questions to help you analyze the research:

• What was the research question of the study you are reviewing? What were the authors trying to discover?
• Was the research funded by a source that could influence the findings?
• What were the research methodologies? Analyze its literature review, the samples and variables used, the results, and the conclusions.
• Does the research seem to be complete? Could it have been conducted more soundly? What further questions does it raise?
• If there are conflicting studies, why do you think that is?
• How are the authors viewed in the field? Has this study been cited? If so, how has it been analyzed?

Tips: 

• Review the abstracts carefully.  
• Keep careful notes so that you may track your thought processes during the research process.
• Create a matrix of the studies for easy analysis, and synthesis, across all of the studies.
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How to do a Literature Search: Introduction

• Introduction
• Choosing a database
• Choosing keywords
• Using keywords
• Author searching
• Managing your search/results

What is a literature review?

You may be asked to write a literature review as part of an undergraduate project or postgraduate dissertation.  A well-conducted literature review will showcase your ability to:

• Survey the literature and select the most important contributions on your topic
• Critically evaluate the literature to identify key developments, trends, issues, gaps in knowledge
• Present your findings in a clear and coherent manner

The structure of a literature review may vary according to your specific subject but it will normally include these three areas:

• Introduction : an overview of your topic explaining why it is important, putting it in the wider context and perhaps highlighting recent progress and future potential.  It may also explain the scope and the organisation of your review.
• Main body : a discussion of how research in the topic has progressed to date, critically evaluating the key studies and explaining their significance.  
• Conclusion : a summary of current knowledge, highlighting any gaps in current knowledge or practice and suggesting how these may be overcome in future research.

Having identified the topic of your review, the first step will be to undertake a literature search .  

What is a literature search?

Define your research question(s).

Before you login to a database to begin your search it's crucial that you analyse your topic, breaking it down into a number of research questions.

Take, for example, this topic:   Are biofuels the answer to falling oil reserves?

You  could  type this sentence into a database search box, but that is usually not helpful, as the sentence may not contain the most appropriate keywords.  Also this single sentence is unlikely to encompass everything that you want to find out.  You need to break down the topic into a number of separate questions and then look for the answers. For this example here are some of the questions you could ask:

• What is a biofuel?  
• How are they made?
• How much of our fuel is already from biofuel (market share)?
• Could we make enough to replace oil and/or gas?
• What are the advantages and disadvantages of using biofuels compared with oil and gas?
• Could we use biofuels for transport?
• What is UK government policy relating to biofuels?

You  may  find the answers to all of these questions using a single search engine such as Google Scholar, or a single Library database, but you are more likely to succeed if you match each question to a relevant source .

Introduction to literature searching

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Writing a Literature Review

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A literature review is a document or section of a document that collects key sources on a topic and discusses those sources in conversation with each other (also called synthesis ). The lit review is an important genre in many disciplines, not just literature (i.e., the study of works of literature such as novels and plays). When we say “literature review” or refer to “the literature,” we are talking about the research ( scholarship ) in a given field. You will often see the terms “the research,” “the scholarship,” and “the literature” used mostly interchangeably.

Where, when, and why would I write a lit review?

There are a number of different situations where you might write a literature review, each with slightly different expectations; different disciplines, too, have field-specific expectations for what a literature review is and does. For instance, in the humanities, authors might include more overt argumentation and interpretation of source material in their literature reviews, whereas in the sciences, authors are more likely to report study designs and results in their literature reviews; these differences reflect these disciplines’ purposes and conventions in scholarship. You should always look at examples from your own discipline and talk to professors or mentors in your field to be sure you understand your discipline’s conventions, for literature reviews as well as for any other genre.

A literature review can be a part of a research paper or scholarly article, usually falling after the introduction and before the research methods sections. In these cases, the lit review just needs to cover scholarship that is important to the issue you are writing about; sometimes it will also cover key sources that informed your research methodology.

Lit reviews can also be standalone pieces, either as assignments in a class or as publications. In a class, a lit review may be assigned to help students familiarize themselves with a topic and with scholarship in their field, get an idea of the other researchers working on the topic they’re interested in, find gaps in existing research in order to propose new projects, and/or develop a theoretical framework and methodology for later research. As a publication, a lit review usually is meant to help make other scholars’ lives easier by collecting and summarizing, synthesizing, and analyzing existing research on a topic. This can be especially helpful for students or scholars getting into a new research area, or for directing an entire community of scholars toward questions that have not yet been answered.

What are the parts of a lit review?

Most lit reviews use a basic introduction-body-conclusion structure; if your lit review is part of a larger paper, the introduction and conclusion pieces may be just a few sentences while you focus most of your attention on the body. If your lit review is a standalone piece, the introduction and conclusion take up more space and give you a place to discuss your goals, research methods, and conclusions separately from where you discuss the literature itself.

Introduction:

• An introductory paragraph that explains what your working topic and thesis is
• A forecast of key topics or texts that will appear in the review
• Potentially, a description of how you found sources and how you analyzed them for inclusion and discussion in the review (more often found in published, standalone literature reviews than in lit review sections in an article or research paper)
• Summarize and synthesize: Give an overview of the main points of each source and combine them into a coherent whole
• Analyze and interpret: Don’t just paraphrase other researchers – add your own interpretations where possible, discussing the significance of findings in relation to the literature as a whole
• Critically Evaluate: Mention the strengths and weaknesses of your sources
• Write in well-structured paragraphs: Use transition words and topic sentence to draw connections, comparisons, and contrasts.

Conclusion:

• Summarize the key findings you have taken from the literature and emphasize their significance
• Connect it back to your primary research question

How should I organize my lit review?

Lit reviews can take many different organizational patterns depending on what you are trying to accomplish with the review. Here are some examples:

• Chronological : The simplest approach is to trace the development of the topic over time, which helps familiarize the audience with the topic (for instance if you are introducing something that is not commonly known in your field). If you choose this strategy, be careful to avoid simply listing and summarizing sources in order. Try to analyze the patterns, turning points, and key debates that have shaped the direction of the field. Give your interpretation of how and why certain developments occurred (as mentioned previously, this may not be appropriate in your discipline — check with a teacher or mentor if you’re unsure).
• Thematic : If you have found some recurring central themes that you will continue working with throughout your piece, you can organize your literature review into subsections that address different aspects of the topic. For example, if you are reviewing literature about women and religion, key themes can include the role of women in churches and the religious attitude towards women.
• Qualitative versus quantitative research
• Empirical versus theoretical scholarship
• Divide the research by sociological, historical, or cultural sources
• Theoretical : In many humanities articles, the literature review is the foundation for the theoretical framework. You can use it to discuss various theories, models, and definitions of key concepts. You can argue for the relevance of a specific theoretical approach or combine various theorical concepts to create a framework for your research.

What are some strategies or tips I can use while writing my lit review?

Any lit review is only as good as the research it discusses; make sure your sources are well-chosen and your research is thorough. Don’t be afraid to do more research if you discover a new thread as you’re writing. More info on the research process is available in our "Conducting Research" resources .

As you’re doing your research, create an annotated bibliography ( see our page on the this type of document ). Much of the information used in an annotated bibliography can be used also in a literature review, so you’ll be not only partially drafting your lit review as you research, but also developing your sense of the larger conversation going on among scholars, professionals, and any other stakeholders in your topic.

Usually you will need to synthesize research rather than just summarizing it. This means drawing connections between sources to create a picture of the scholarly conversation on a topic over time. Many student writers struggle to synthesize because they feel they don’t have anything to add to the scholars they are citing; here are some strategies to help you:

• It often helps to remember that the point of these kinds of syntheses is to show your readers how you understand your research, to help them read the rest of your paper.
• Writing teachers often say synthesis is like hosting a dinner party: imagine all your sources are together in a room, discussing your topic. What are they saying to each other?
• Look at the in-text citations in each paragraph. Are you citing just one source for each paragraph? This usually indicates summary only. When you have multiple sources cited in a paragraph, you are more likely to be synthesizing them (not always, but often
• Read more about synthesis here.

The most interesting literature reviews are often written as arguments (again, as mentioned at the beginning of the page, this is discipline-specific and doesn’t work for all situations). Often, the literature review is where you can establish your research as filling a particular gap or as relevant in a particular way. You have some chance to do this in your introduction in an article, but the literature review section gives a more extended opportunity to establish the conversation in the way you would like your readers to see it. You can choose the intellectual lineage you would like to be part of and whose definitions matter most to your thinking (mostly humanities-specific, but this goes for sciences as well). In addressing these points, you argue for your place in the conversation, which tends to make the lit review more compelling than a simple reporting of other sources.

Finding Information: Systematic Searches for Health

• Finding Information
• The Search Process
• Preparing to Search
• Understanding Your Information Need
• Understanding the Question
• Conducting Scoping Searches
• Generating Keywords and Alternative Terms
• Search Tools and Resources
• Specialist Resources
• The Open Web
• Artificial Intelligence (AI) Tools
• Enhancing Your Search
• Search Techniques
• Saving Your Search
• Citation Searching
• Selecting Your Sources
• Accessing the Full Text
• Assessing and Improving Result Relevance
• Assessing and Improving Result Quality
• Identifying Information Gaps
• Literature Reviews and Systematic Searches
• Systematic Searches for Health

Introduction to Systematic Searches for Health

This guide is designed to help you complete a systematic literature search for literature in health subjects. You will most likely have to complete a search in this way for research methods modules and your dissertation. Please note that this is a general guide ; you should always check in with your course team, supervisor, and assignment documentation to clarify aims and expectations. 

As well as being a large component of your assignment or dissertation, systematic searches of this kind...

“Are becoming ever more important in health and social care. The growing importance of evidence-based practice (EBP) within health and social care today has led to literature reviews becoming more relevant to current practice."  Aveyard, H. (2023) Doing a literature review in health and social care: a practical guide. 5th edn. London: Open University Press.

Features of a Systematic Search in Health

A systematic search for health has some similar components to a general literature search, but there are a few things that are done differently. This is because in order to be a rigorous research method, the search needs to be carried out and presented in a systematic and thorough way. 

For example, in your dissertation, you may need to include elements such as: 

• PEO/PICO table 
• Inclusion/exclusion criteria 
• Search table 
• PRISMA flow chart 

All of these elements, along with your commentary on the search, provides a clear picture of how you planned and executed your search . Importantly, the search table in particular allows your search to be replicable by others. 

Doing Your Systematic Search

Introduction.

• Step 1: Scope the Literature
• Step 2: Formulate your question
• Step 3: Develop your search terms
• Step 4: Apply search techniques
• Step 5: Select your databases
• Step 6: Refine your results
• Step 7: Select your articles
• Step 8: Present your search results
• Step 9: What next?

This section gives a breakdown of the steps you will need to take in order to complete the search process. It can be helpful to break the process down in this way so you can see what is needed and tackle it one step at a time.

However, the search process is not always this straightforward: it is an iterative process. Don't be disheartened if you move back and forth through the steps before you finalise your search and choose your final articles. For a more detailed description of the search process see our guide here . 

Scope the Literature

Background or scoping searches are preliminary searches of the literature for information surrounding your topic before you start your structured, systematic literature search. It can help you to gain an understanding of the topic, look at what literature is available, and think about what keywords you might use in your final search. 

To get more information about how to do a background (or scoping) search, see our guidance here .  

You can use your background search to narrow down your topic. For example, you may have a general topic that you are interested in. When you start to explore the literature, recurring themes may appear. You could use one or more of these themes to focus and refine your question.  

Formulate Your Question

After you have done a background search and got a better idea of your research topic, you will need to translate it into a  question. Tools which you can help you to formulate your question include the PICO and PEO frameworks.

The PEO and PICO frameworks are used widely in nursing and health research and in professional practice. They are strongly advocated by the NHS. They help you to formulate an answerable question and to identify the key concepts within it. They also help you to develop your inclusion and exclusion criteria and you should refer back to these when you are making your final selection of articles. 

Which framework you choose will depend on the nature of your question. Generally, PEO is used for qualitative questions and PICO for quantitative ones. Look at the descriptions below for more information on each. 

The PEO framework lends itself more to qualitative research. 

Example question: 

What are the attitudes of health professionals towards caring for older patients with dementia in an acute setting?

PICO is mainly used for quantitative research and allows for comparison between interventions. 

How effective are pressure garments in the treatment of leg ulcers?

Test your knowledge of PICO and PEO with the quick quiz below . For each example, pick whether you think you would use PICO or PEO as your chosen framework. 

Develop Your Search Terms

Now you can start to construct your search strings. Search strings are made up of keywords from your question with alternative terms as appropriate. Look at our guide on generating keywords and alternative terms for more information.

Remember, search terms represent the main concepts from your question . While they will be grounded in PICO/PEO, they do not need to follow exactly the same structure as PEO/PICO - this can result in poor and inconsistent results.

Test your knowledge with the below activity. 

You have formulated a question and PICO table. You now need to construct your search strings. Which of the following would you choose, and why?

P: patients with suspected sepsis in the pre-hospital setting

I: pre-hospital antibiotics 

O: impact on mortality rates 

Apply Search Techniques

Once you have decided on your search terms, you will combine them using Boolean Operators . You may also wish to utilise additional advanced search techniques like truncation, phrase searching, wildcards, and proximity search. See our Enhancing Your Search guide for further guidance . 

Click on the image below to see where search techniques have been added to improve this search.

Select Your Databases

When researching your dissertation, you are expected to search across multiple databases (usually three). To learn more about our database collection, click here . Be sure to confirm the exact number by taking a look at your course handbook, corresponding with your course team, or having a chat with your supervisor. 

Go to the A-Z of eResources  to find out what databases are available in your discipline. Filter by your subject area and then look through the list. Each database will have a description of what is included. Use this to help you decide which ones to try. 

You will notice that the layout of the databases can vary slightly. Below are a few videos showing how to search in a few of the most-used databases. 

British Nursing Database 

Refine Your Results

Once you are happy with your search strings and have tried them out in a database, it is very likely that you will need to refine your results in some way. What you need to do next will depend on the results you end up with. For example, do you have too many results? Too few? Are they relevant to your topic? 

Explore the below pages to decide whether your sources are appropriate, and how you might refine them further, then have a look at the information below next steps: 

• Limiters and Field Searching
• Assessing/Improving Source Relevance
• Assessing/Improving Source Quality

How many results should I have? 

This is a very common question, without an exact answer.

You need enough relevant articles to have a little choice in what you select, but not so many that you're overwhelmed. The aim is to be able to look through at least the title and ideally the abstract of every article in your result list. This allows you to select your articles in a systematic and informed way. Can you realistically do this? If not, consult the links above to help you refine your result set.   

Select Your Articles

By now you have completed your search in your chosen database(s). You’ve refined the results and are happy with the number and relevance. Be sure to read through our guidance on Selecting your Sources if you need a little more help with refining your results. 

Now it’s time to select your final set of articles for your review. This number will vary widely depending on your assignment, level, and course of study. Confirm how many papers you need with your course team, supervisor, or by checking your course handbook.

Inclusion and Exclusion Criteria 

You must select and exclude articles based on recorded inclusion and exclusion criteria. 

• Inclusion criteria  are predefined characteristics or criteria used to determine which studies should be included in a research synthesis process. They help ensure that selected studies align with the research question and objectives, and they typically include factors such as study population, interventions, outcomes, and study design.
• Exclusion criteria in literature searching are predefined characteristics or criteria used to identify and exclude studies that do not meet specific requirements from a research synthesis process. These criteria help researchers exclude studies that may introduce bias or lack relevance to the research question, improving the quality and focus of the synthesis.

You will determine your inclusion and exclusion criteria based on the parameters of your topic and PEO/PICO table. You will produce a table with two columns detailing your inclusion and exclusion criteria, which will be included in your final dissertation. You may also use your inclusion and exclusion criteria to help you produce a PRISMA flow diagram. 

See the activity below for an example and to test your knowledge. 

Present Your Search Results

One element of your systematic search which is specific to health subjects is the presentation of your search strings and results in a table. This makes it clear what you have searched for and where, what limits you applied and how many results you ended up with.  Your search table makes your search process clear and replicable to anyone reading your assignment or dissertation. 

You should complete the final version of this table at the end of the search once you are completely happy with it and are confident that you have an appropriate number of relevant results. 

To complete your search table, you will need to follow the below steps: 

• Search each individual string on its own in each of your selected databases. Record the number of search results for each string and database. 
• Search all strings in combination in each of your selected databases. Record the number of search results for each database. 
• Apply equivalent filters in each of your selected databases. Record the number of search results  for each database. 

Not sure how to present your search table? Download the files below. 

• Presenting your search table Download this file for examples of search table.
• Editable search table template Download this file for a search table template which you can edit with your own search strings and results.

What next? 

Well done! You’ve completed your systematic search and presented your results in a table. What next? 

In addition to the search information (PICO/PEO, search table, inclusion and exclusion criteria) you will often need to present information about how you selected your articles from the final set of results ( PRISMA Flow Diagram ) and then include a critique of the articles ( CASP/Holland and Rees ). A brief introduction to both of these is included below. 

A Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) flow chart is a diagram that depicts the flow of information through the different phases of your systematic search. It shows the number of records identified, included, and excluded, and the reasons for exclusions.

The PRISMA flow chart has different boxes and arrows that connect them. The boxes show the different steps, like finding studies, screening them, and deciding which ones to include or exclude. The arrows show how many studies are involved at each step. The flow chart is important because it helps you show how you chose the studies and if there were any problems or biases in the process. More information and examples can be found on the PRISMA website.

• PRISMA guide A guide to creating your PRISMA flowchart with an explanation of the steps, blank template and an example.

Critiquing frameworks

Always check with your tutor or supervisor as to whether they have a preference for a particular framework. Here are two that are commonly used. 

The Critical Appraisal Skills Programme (CASP) tool helps people evaluate research papers in healthcare. It uses a step-by-step approach and asks questions about things like how the study was done and what the results mean. By using CASP, you can figure out if a study is reliable and can be used to make decisions. 

More information, examples and template CASP checklists can be found on their website.

Holland and Rees

Another available framework is from Holland and Rees' book Nursing: Evidence-based practice skills  (linked below). 

Their frameworks for critiquing quantitative or qualitative articles can be found here. 

More information can be found by looking at the book. Follow the link below to see its availability in the library. 

Further Reading

• Searching the Literature
• Understanding the Literature
• Writing Your Health Dissertation

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• Indian J Anaesth
• v.60(9); 2016 Sep

Literature search for research planning and identification of research problem

Anju grewal.

Department of Anaesthesiology, Dayanand Medical College and Hospital, Ludhiana, Punjab, India

Hanish Kataria

1 Department of Surgery, Government Medical College and Hospital, Chandigarh, India

2 Department of Cardiac Anaesthesia, All India Institute of Medical Sciences, New Delhi, India

Literature search is a key step in performing good authentic research. It helps in formulating a research question and planning the study. The available published data are enormous; therefore, choosing the appropriate articles relevant to your study in question is an art. It can be time-consuming, tiring and can lead to disinterest or even abandonment of search in between if not carried out in a step-wise manner. Various databases are available for performing literature search. This article primarily stresses on how to formulate a research question, the various types and sources for literature search, which will help make your search specific and time-saving.

INTRODUCTION

Literature search is a systematic and well-organised search from the already published data to identify a breadth of good quality references on a specific topic.[ 1 ] The reasons for conducting literature search are numerous that include drawing information for making evidence-based guidelines, a step in the research method and as part of academic assessment.[ 2 ] However, the main purpose of a thorough literature search is to formulate a research question by evaluating the available literature with an eye on gaps still amenable to further research.

Research problem[ 3 ] is typically a topic of interest and of some familiarity to the researcher. It needs to be channelised by focussing on information yet to be explored. Once we have narrowed down the problem, seeking and analysing existing literature may further straighten out the research approach.

A research hypothesis[ 4 ] is a carefully created testimony of how you expect the research to proceed. It is one of the most important tools which aids to answer the research question. It should be apt containing necessary components, and raise a question that can be tested and investigated.

The literature search can be exhaustive and time-consuming, but there are some simple steps which can help you plan and manage the process. The most important are formulating the research questions and planning your search.

FORMULATING THE RESEARCH QUESTION

Literature search is done to identify appropriate methodology, design of the study; population sampled and sampling methods, methods of measuring concepts and techniques of analysis. It also helps in determining extraneous variables affecting the outcome and identifying faults or lacunae that could be avoided.

Formulating a well-focused question is a critical step for facilitating good clinical research.[ 5 ] There can be general questions or patient-oriented questions that arise from clinical issues. Patient-oriented questions can involve the effect of therapy or disease or examine advantage versus disadvantage for a group of patients.[ 6 ]

For example, we want to evaluate the effect of a particular drug (e.g., dexmedetomidine) for procedural sedation in day care surgery patients. While formulating a research question, one should consider certain criteria, referred as ‘FINER’ (F-Feasible, I-Interesting, N-Novel, E-Ethical, R-Relevant) criteria.[ 5 ] The idea should be interesting and relevant to clinical research. It should either confirm, refute or add information to already done research work. One should also keep in mind the patient population under study and the resources available in a given set up. Also the entire research process should conform to the ethical principles of research.

The patient or study population, intervention, comparison or control arm, primary outcome, timing of measurement of outcome (PICOT) is a well-known approach for framing a leading research question.[ 7 , 8 ] Dividing the questions into key components makes it easy and searchable. In this case scenario:

• Patients (P) – What is the important group of patients? for example, day care surgery
• Intervention (I) – What is the important intervention? for example, intravenous dexmedetomidine
• Comparison (C) – What is the important intervention of comparison? for example, intravenous ketamine
• Outcome (O) – What is the effect of intervention? for example, analgesic efficacy, procedural awareness, drug side effects
• Time (T) – Time interval for measuring the outcome: Hourly for first 4 h then 4 hourly till 24 h post-procedure.

Multiple questions can be formulated from patient's problem and concern. A well-focused question should be chosen for research according to significance for patient interest and relevance to our knowledge. Good research questions address the lacunae in available literature with an aim to impact the clinical practice in a constructive manner. There are limited outcome research and relevant resources, for example, electronic database system, database and hospital information system in India. Even when these factors are available, data about existing resources is not widely accessible.[ 9 ]

TYPES OF MEDICAL LITERATURE

(Further details in chapter ‘Types of studies and research design’ in this issue).

Primary literature

Primary sources are the authentic publication of an expert's new evidence, conclusions and proposals (case reports, clinical trials, etc) and are usually published in a peer-reviewed journal. Preliminary reports, congress papers and preprints also constitute primary literature.[ 2 ]

Secondary literature

Secondary sources are systematic review articles or meta-analyses where material derived from primary source literature are infererred and evaluated.[ 2 ]

Tertiary literature

Tertiary literature consists of collections that compile information from primary or secondary literature (eg., reference books).[ 2 ]

METHODS OF LITERATURE SEARCH

There are various methods of literature search that are used alone or in combination [ Table 1 ]. For past few decades, searching the local as well as national library for books, journals, etc., was the usual practice and still physical literature exploration is an important component of any systematic review search process.[ 10 , 11 ] With the advancement of technology, the Internet is now the gateway to the maze of vast medical literature.[ 12 ] Conducting a literature review involves web-based search engines, i.e., Google, Google Scholar, etc., [ Table 2 ], or using various electronic research databases to identify materials that describe the research topic or those homologous to it.[ 13 , 14 ]

Methods of literature search

Web based methods of literature search

The various databases available for literature search include databases for original published articles in the journals [ Table 2 ] and evidence-based databases for integrated information available as systematic reviews and abstracts [ Table 3 ].[ 12 , 14 ] Most of these are not freely available to the individual user. PubMed ( http://www.ncbi.nlm.nih.gov/pubmed/ ) is the largest available resource since 1996; however, a large number of sources now provide free access to literature in the biomedical field.[ 15 ] More than 26 million citations from Medline, life science journals and online books are included in PubMed. Links to the full-text material are included in citations from PubMed Central and publisher web sites.[ 16 ] The choice of databases depends on the subject of interest and potential coverage by the different databases. Education Resources Information Centre is a free online digital library of education research and information sponsored by the Institute of Education Sciences of the U.S. Department of Education, available at http://eric.ed.gov/ . No one database can search all the medical literature. There is need to search several different databases. At a minimum, PubMed or Medline, Embase and the Cochrane central trials Registry need to be searched. When searching these databases, emphasis should be given to meta-analysis, systematic reviews randomised controlled trials and landmark studies.

Electronic source of Evidence-Based Database

Time allocated to the search needs attention as exploring and selecting data are early steps in the research method and research conducted as part of academic assessment have narrow timeframes.[ 17 ] In Indian scenario, limited outcome research and accessibility to data leads to less thorough knowledge of nature of research problem. This results in the formulation of the inappropriate research question and increases the time to literature search.

TYPES OF SEARCH

Type of search can be described in different forms according to the subject of interest. It increases the chances of retrieving relevant information from a search.

Translating research question to keywords

This will provide results based on any of the words specified; hence, they are the cornerstone of an effective search. Synonyms/alternate terms should be considered to elicit further information, i.e., barbiturates in place of thiopentone. Spellings should also be taken into account, i.e., anesthesia in place of anaesthesia (American and British). Most databases use controlled word-stock to establish common search terms (or keywords). Some of these alternative keywords can be looked from database thesaurus.[ 4 ] Another strategy is combining keywords with Boolean operators. It is important to keep a note of keywords and methods used in exploring the literature as these will need to be described later in the design of search process.

‘Medical Subject Heading (MeSH) is the National Library of Medicine's controlled hierarchical vocabulary that is used for indexing articles in PubMed, with more specific terms organised underneath more general terms’.[ 17 ] This provides a reliable way to retrieve citations that use different terminology for identical ideas, as it indexes articles based on content. Two features of PubMed that can increase yield of specific articles are ‘Automatic term mapping’ and ‘automatic term explosion’.[ 4 ]

For example, if the search keyword is heart attack, this term will match with MeSH transcription table heading and then explode into various subheadings. This helps to construct the search by adding and selecting MeSH subheadings and families of MeSH by use of hyperlinks.[ 4 ]

We can set limits to a clinical trial for retrieving higher level of evidence (i.e., randomised controlled clinical trial). Furthermore, one can browse through the link entitled ‘Related Articles’. This PubMed feature searches for similar citations using an intricate algorithm that scans titles, abstracts and MeSH terms.[ 4 ]

Phrase search

This will provide pages with only the words typed in the phrase, in that exact order and with no words in between them.

Boolean operators

AND, OR and NOT are the three Boolean operators named after the mathematician George Boole.[ 18 ] Combining two words using ‘AND’ will fetch articles that mention both the words. Using ‘OR’ will widen the search and fetch more articles that mention either subject. While using the term ‘NOT’ to combine words will fetch articles containing the first word but not the second, thus narrowing the search.

Filters can also be used to refine the search, for example, article types, text availability, language, age, sex and journal categories.

Overall, the recommendations for methodology of literature search can be as below (Creswell)[ 19 ]

• Identify keywords and use them to search articles from library and internet resources as described above
• Search several databases to search articles related to your topic
• Use thesaurus to identify terms to locate your articles
• Find an article that is similar to your topic; then look at the terms used to describe it, and use them for your search
• Use databases that provide full-text articles (free through academic libraries, Internet or for a fee) as much as possible so that you can save time searching for your articles
• If you are examining a topic for the first time and unaware of the research on it, start with broad syntheses of the literature, such as overviews, summaries of the literature on your topic or review articles
• Start with the most recent issues of the journals, and look for studies about your topic and then work backward in time. Follow-up on references at the end of the articles for more sources to examine
• Refer books on a single topic by a single author or group of authors or books that contain chapters written by different authors
• Next look for recent conference papers. Often, conference papers report the latest research developments. Contact authors of pertinent studies. Write or phone them, asking if they know of studies related to your area of interest
• The easy access and ability to capture entire articles from the web make it attractive. However, check these articles carefully for authenticity and quality and be cautious about whether they represent systematic research.

The whole process of literature search[ 20 ] is summarised in Figure 1 .

Process of literature search

Literature search provides not only an opportunity to learn more about a given topic but provides insight on how the topic was studied by previous analysts. It helps to interpret ideas, detect shortcomings and recognise opportunities. In short, systematic and well-organised research may help in designing a novel research.

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How to Find Sources | Scholarly Articles, Books, Etc.

Published on June 13, 2022 by Eoghan Ryan . Revised on May 31, 2023.

It’s important to know how to find relevant sources when writing a  research paper , literature review , or systematic review .

The types of sources you need will depend on the stage you are at in the research process , but all sources that you use should be credible , up to date, and relevant to your research topic.

There are three main places to look for sources to use in your research:

Research databases

• Your institution’s library
• Other online resources

Table of contents

Library resources, other online sources, other interesting articles, frequently asked questions about finding sources.

You can search for scholarly sources online using databases and search engines like Google Scholar . These provide a range of search functions that can help you to find the most relevant sources.

If you are searching for a specific article or book, include the title or the author’s name. Alternatively, if you’re just looking for sources related to your research problem , you can search using keywords. In this case, it’s important to have a clear understanding of the scope of your project and of the most relevant keywords.

Databases can be general (interdisciplinary) or subject-specific.

• You can use subject-specific databases to ensure that the results are relevant to your field.
• When using a general database or search engine, you can still filter results by selecting specific subjects or disciplines.

Example: JSTOR discipline search filter

Check the table below to find a database that’s relevant to your research.

Google Scholar

To get started, you might also try Google Scholar , an academic search engine that can help you find relevant books and articles. Its “Cited by” function lets you see the number of times a source has been cited. This can tell you something about a source’s credibility and importance to the field.

Example: Google Scholar “Cited by” function

Boolean operators

Boolean operators can also help to narrow or expand your search.

Boolean operators are words and symbols like AND , OR , and NOT that you can use to include or exclude keywords to refine your results. For example, a search for “Nietzsche NOT nihilism” will provide results that include the word “Nietzsche” but exclude results that contain the word “nihilism.”

Many databases and search engines have an advanced search function that allows you to refine results in a similar way without typing the Boolean operators manually.

Example: Project Muse advanced search

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You can find helpful print sources in your institution’s library. These include:

• Journal articles
• Encyclopedias
• Newspapers and magazines

Make sure that the sources you consult are appropriate to your research.

You can find these sources using your institution’s library database. This will allow you to explore the library’s catalog and to search relevant keywords. You can refine your results using Boolean operators .

Once you have found a relevant print source in the library:

• Consider what books are beside it. This can be a great way to find related sources, especially when you’ve found a secondary or tertiary source instead of a primary source .
• Consult the index and bibliography to find the bibliographic information of other relevant sources.

You can consult popular online sources to learn more about your topic. These include:

• Crowdsourced encyclopedias like Wikipedia

You can find these sources using search engines. To refine your search, use Boolean operators in combination with relevant keywords.

However, exercise caution when using online sources. Consider what kinds of sources are appropriate for your research and make sure the sites are credible .

Look for sites with trusted domain extensions:

• URLs that end with .edu are educational resources.
• URLs that end with .gov are government-related resources.
• DOIs often indicate that an article is published in a peer-reviewed , scientific article.

Other sites can still be used, but you should evaluate them carefully and consider alternatives.

If you want to know more about ChatGPT, AI tools , citation , and plagiarism , make sure to check out some of our other articles with explanations and examples.

• ChatGPT vs human editor
• ChatGPT citations
• Is ChatGPT trustworthy?
• Using ChatGPT for your studies
• What is ChatGPT?
• Chicago style
• Paraphrasing

 Plagiarism

• Types of plagiarism
• Self-plagiarism
• Avoiding plagiarism
• Academic integrity
• Consequences of plagiarism
• Common knowledge

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You can find sources online using databases and search engines like Google Scholar . Use Boolean operators or advanced search functions to narrow or expand your search.

For print sources, you can use your institution’s library database. This will allow you to explore the library’s catalog and to search relevant keywords.

It is important to find credible sources and use those that you can be sure are sufficiently scholarly .

• Consult your institute’s library to find out what books, journals, research databases, and other types of sources they provide access to.
• Look for books published by respected academic publishing houses and university presses, as these are typically considered trustworthy sources.
• Look for journals that use a peer review process. This means that experts in the field assess the quality and credibility of an article before it is published.

When searching for sources in databases, think of specific keywords that are relevant to your topic , and consider variations on them or synonyms that might be relevant.

Once you have a clear idea of your research parameters and key terms, choose a database that is relevant to your research (e.g., Medline, JSTOR, Project MUSE).

Find out if the database has a “subject search” option. This can help to refine your search. Use Boolean operators to combine your keywords, exclude specific search terms, and search exact phrases to find the most relevant sources.

There are many types of sources commonly used in research. These include:

You’ll likely use a variety of these sources throughout the research process , and the kinds of sources you use will depend on your research topic and goals.

Scholarly sources are written by experts in their field and are typically subjected to peer review . They are intended for a scholarly audience, include a full bibliography, and use scholarly or technical language. For these reasons, they are typically considered credible sources .

Popular sources like magazines and news articles are typically written by journalists. These types of sources usually don’t include a bibliography and are written for a popular, rather than academic, audience. They are not always reliable and may be written from a biased or uninformed perspective, but they can still be cited in some contexts.

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