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Literature Search: Databases and Gray Literature

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. 


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

  • Gray Literature is the term for information that falls outside the mainstream of published journal and mongraph literature, not controlled by commercial publishers
  • includes:
    • 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    • clinical trials - ongoing or unpublished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