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Systematic Reviews: Grey literature

Mae'r dudalen hon hefyd ar gael yn Gymraeg

What is Grey literature?

Grey literature refers to both published and unpublished research material that is not available commercially. A systematic review can be biased when it fails to report crucial information that may be hidden in some grey literature. A search of grey literature is one way to address potentially biased reporting of research results in published material.
Some examples of grey literature are:

  • conference papers/conference proceedings
  • theses
  • clinical trials
  • newsletters
  • pamphlets
  • reports
  • fact sheets, bulletins
  • government documents
  • surveys
  • interviews
  • informal communication (e.g. blogs, podcasts, email)

Grey literature can be the best source of up-to-date research on some topics note however that grey literature is usually not subject to peer review and must be evaluated accordingly.

General sources of Grey literature

Conference Abstracts & Proceedings

Conference abstracts & proceeding

  • Search of conference web pages
  • Hand-search of published conference proceedings

Trial Registers

  • Trials registers
    • Country specific registries & pharmaceutical registries
    • Other registries are available and may be worth consulting depending on your subject