The Literature Search
- A systematic review search includes a search of databases, gray literature, personal communications, and a handsearch of high impact journals in the related field. See our list of recommended databases and gray literature sources on this page.
- a comprehensive literature search can not be dependent on a single database, nor on bibliographic databases only.
- inclusion of multiple databases helps avoid publication bias (georaphic bias or bias against publication of negative results).
- The Cochrane Collaboration recommends PubMed, Embase and the Cochrane Central Register of Controlled Trials (CENTRAL) at a minimum.
- NOTE: The Cochrane Collaboration and the IOM recommend that the literature search be conducted by librarians or persons with extensive literature search experience. Please contact the NIH Librarians for assistance with the literature search component of your systematic review.
- Cochrane Library
A collection of six databases that contain different types of high-quality, independent evidence to inform healthcare decision-making. Search the Cochrane Central Register of Controlled Trials here.
European database of biomedical and pharmacologic literature.
PubMed comprises more than 21 million citations for biomedical literature from MEDLINE, life science journals, and online books.
Largest abstract and citation database of peer-reviewed literature and quality web sources. Contains conference papers.
- Web of Science
World's leading citation databases. Covers over 12,000 of the highest impact journals worldwide, including Open Access journals and over 150,000 conference proceedings. Coverage in the sciences, social sciences, arts, and humanities, with coverage to 1900.
Subject Specific Databases
- APA PsycINFO
Over 4.5 million abstracts of peer-reviewed literature in the behavioral and social sciences. Includes conference papers, book chapters, psychological tests, scales and measurement tools.
- CINAHL Plus
Comprehensive journal index to nursing and allied health literature, includes books, nursing dissertations, conference proceedings, practice standards and book chapters.
Latin American and Caribbean health sciences literature database
- Gray Literature is the term for information that falls outside the mainstream of published journal and mongraph literature, not controlled by commercial publishers
- hard to find studies, reports, or dissertations
- conference abstracts or papers
- governmental or private sector research
- clinical trials - ongoing or unpublished
- experts and researchers in the field
- Gray Literature Sources
- Library catalogs
- Professional association websites
- WorldCat - 1.5 billion items in this collection of library catalogs
- Google Scholar - Search scholarly literature across many disciplines and sources, including theses, books, abstracts and articles.
- Dissertation Abstracts - dissertation and theses database - NIH Library biomedical librarians can access and search for you.
- NTIS - central resource for government-funded scientific, technical, engineering, and business related information.
- AHRQ - agency for healthcare research and quality
- Open Grey - system for information on grey literature in Europe. Open access to 700,000 references to the grey literature.
- World Health Organization - providing leadership on global health matters, shaping the health research agenda, setting norms and standards, articulating evidence-based policy options, providing technical support to countries and monitoring and assessing health trends.
- New York Academy of Medicine Grey Literature Report - a bimonthly publication of The New York Academy of Medicine (NYAM) alerting readers to new gray literature publications in health services research and selected public health topics. NOTE: Discontinued as of Jan 2017, but resources are still accessible.
- Gray Source Index
- OpenDOAR - directory of academic repositories
Clinical Trial Registries
- International Clinical Trials Registery Platform - from the World Health Organization
- Australian New Zealand Clinical Trials Registry
- Brazilian Clinical Trials Registry
- Chinese Clinical Trial Registry-
- ClinicalTrials.gov - U.S. and international federally and privately supported clinical trials registry and results database
- Clinical Trials Registry - India
- EU clinical Trials Register
- Japan Primary Registries Network
- Pan African Clinical Trials Registry