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.
- 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- clinical trials - ongoing or unpublished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
- 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.
- List Gray Literature Producing Organizations - from the New York Academy of Medicine, includes government and private sector
- 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
NIH Library Service: