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Systematic & Evidence Synthesis Reviews: Search

Basic information on types of "knowledge syntheses"/systematic reviews to help users plan the best review type, team, methods and have a clear sense of the expectations/responsibilities of performing these comprehensive literature review projects.

Search Term Brainstorming

A good comprehensive search strategy includes two kinds of search terms: keywords (any words or phrases that you choose) and subject headings (specific terms created by the database to represent particular concepts).  Having multiple search terms for each of your concepts ensures that your search strategy captures all literature relevant to your question.  The goal of a systematic review is to retrieve a comprehensive collection of literature, not just from authors who'd have used the same words, word forms, spelling and hyphenization as you.

If you feel stuck, there are several sources available to help you discover additional search terms: 

  • Abstracts/full texts of pre-identified relevant articles and results of preliminary searches on your topic
  • Relevant broader and narrower subject headings in different databases
  • Yale MeSH Analyzer: copy in a description of your topic (potentially your protocol) to have a list of relevant MeSH (PubMed's subject headings) suggested for you.
  • Experts on the topic, including your librarian
  • Textbooks on the topic

Manual/Table of Contents Searching


  1. Select 1 or 2 journals on topics related to the review question
  2. Scan at least Tables of Content of several issues in your publication date range of  selected journals for possibly-missed studies


  1. Captures publications in journals not indexed in databases
  2. Catches formats/sections of journals not indexed in databases: news, supplements, editorials, letters, conference proceedings
  3. Ensures thorough retrieval of relevant articles that would be otherwise missed, particularly when searching difficult-to-describe topics


What it is: 
Tracking citations from one article to another:
  • Backtracking: checking reference lists of selected articles to locate other articles of importance
  • Forward tracking: investigating articles that cited a selected article
  • ID important articles predating online literature databases or not indexed in them
  • Locate newer literature
  • Understand connections as literature on topic developed
  • Identify experts/authors who publish most on topic
Databases that Enable Forward Tracking of Citations:
  • Web of Science (check the Cited References links in the full record of the article of interest)
  • PubMed (check the Cited by list in the full record of the article of interest - only includes PubMed Central articles)
  • ResearchGate (check the Citations tab of the article of interest)
  • Google Scholar (click the Cited By link under the article record)
  • Scopus (click to view all citing documents in the full record of the article of interest)
  • Dimensions (scroll down to Publication Citation in the full record of the article of interest)

Database Selection

Commonly Utilized* in Systematic Review Searches

*Some publishers require searching of particular databases for systematic reviews, check the requirements of your target publishing venue

Specialized Databases (consult a librarian for recommendations)

  • BIOSIS for bioscience/basic sciences 
  • CINAHL for Nursing or Allied Health (OT, PT, SLP, HSA) 
  • APA PsycINFO for psychology, memory, perception, thinking and psychosocial aspects of physical conditions
  • CABI for global health, OneHealth
  • SportDISCUS for nutrition, physical activity/exercise
  • IPA for pharmacology

Grey literature sources

"Grey literature" refers to formats that are not published in the traditional book/journal medium or indexed in bibliographic databases.

Studies have shown that articles with positive results from respected institutions by well-known authors in English or from a developed country are more likely to be published than other articles. Seeking grey literature helps ensure that the results of a comprehensive review are as objective and free from of this publication bias as possible.  Formats include:


  • Clinical Trials (US NIH)
  • NIH RePORTER UF NIH-only trials. Search by project start/end date, funding mechanism, country, PI, publications. Results include link to "similar projects".
  • World Health Organization's International Clinical Trials Registry Platform search by condition, intervention, recruitment status or countries, primary sponsor, phase.
  • ISRCTN Register proposed, ongoing or comleted Browse by body system or Advanced search for condition, internention, funder, etc.
  • Center Watch Industry-support global clinical trials. Patient focus. Started 1994.
  • Australian New Zealand Clinical Trials Registry - voluntary registriaton, publicly owned, managed by non-profit., trials in A/NZ "or elsewhere". Search by intervention or allocation type, gender, age, countries, sponsorship, funding type, phase, registration/trial start dates. Pharmaceuticals, surgical procedures, preventive measures, lifestyle, devices, complementary therapies, tx and rehab strategies.
  • EU Clinical Trials Register open and closed interventional clinical trials in EU or European Economic Area or outside of those but linked to European pediatric medicine. Advanced Search's Search Tools allows limiting by age range, trial status or phase, gender, date range, with or without results.


  • Web of Science database on HSCL Databases Page in Quick Picks table at top of page - search topic, then in left sidebar of results, look under Document Types, perhaps its More Options, click Proceedings or Proceedings Papers, then click Refine.
  • ProceedingsFirst database on ALL HSCL databases page




  • OpenGrey Open Access to 1M+ citations to theses, doctoral dissertations, research reports, some conference papers and official publication in science, technology, biomedical science, economics, social science and humanities. European focus.
  • GreySource select web-based grey lit from GreyNet International
  • Directory of Open Access Repositories (known as OpenDOAR)
  • Registry of Open Access Repositories European
  • GreyNet 1992-2012 From Grey Literature Information Service, Amsterdam, Nederlands.
  • GreySource Only web-based resources that explicitly refer to the term grey literature (or its equivalent in any language) are listed.
  • OAISTER OAIster is a union catalog of millions of records representing open access resources that was built by harvesting from open access collections worldwide using the Open Archives Initiative Protocol for Metadata Harvesting (OAI-PMH).
  • Unpublished Literature Bank CES Web site offers access to unpublished documents (also referred to as Grey Literature) which may be of interest to evaluators.
  • MedNar Free medically-focused deep web search engine that searches publically available authoritative medical and health resources that generally cannot be found through a typical Google search. Results include both black and grey literature.


  • NIOSH-2, National Center for Occupational Safety and Health  National Institute for Occupational Safety and Health, Centers for Disease Control and Prevention. NIOSHTIC-2 is a searchable bibliographic database of occupational safety and health publications, documents, grant reports, and other communication products supported in whole or in part by NIOSH. NIOSHTIC-2 contains 54,198 total citations.
  • NTIS National Technical Information Service Documents in the NTIS Technical Reports collection are the results of federally funded research. They are directly submitted to or collected by NTIS from Federal agencies for permanent accessibility to industry, academia and the public. Before purchasing from NTIS, you may want to check for free access from (1) the issuing organization's website; (2) the U.S. Government Publishing Office's Federal Digital System website; (3) the federal government Internet portal; or (4) a web search conducted using a commercial search engine such as
  • searches over 45 databases and over 2000 selected websites from 14 federal agencies, offering 200 million pages of authoritative U.S. government science information including research and development results.

Clinical Trials Sources

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