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Systematic Reviews: Grey literature

A guide to assist staff and students undertaking systematic reviews

What is grey literature?

Grey literature refers to both published and unpublished research material that is not available commercially. It can be the best source of up-to-date research on some topics. e.g Statistics relating to Australian health. Note however that grey literature is usually not subject to peer review and must be evaluated accordingly. Grey literature can be found by searching the internet, databases, institutional repositories and catalogues. 

Grey literature consists of:

  • reports (reports of government and research organisations, are generally freely available on the internet) 
  • theses
  • conference proceedings
  • technical specifications & standards
  • translations
  • bibliographies 
  • technical & commercial documention 
  • official documents  

Alberani, V., De Castro Pietrangeli, P. & Mazza, A.M.  (1990).  The use of grey literature in health sciences: A preliminary survey.  Bulletin of the Medical Library Association, 78 (4) : 358-363.

Tips for Searching for Grey Literature

In addition to the sources listed above, internet searching can locate other useful sources:

  • If looking for information on grey literature in general, remember there are two spellings and search for (gray OR grey) literature
  • Find and search the online catalogues of large libraries
  • Conference papers or conference proceedings can be difficult to track down - search for the host sites of conferences and academic associations
  • You can search for conference papers in SCOPUS or Web of Science databases.
  • Try restricting your search to the .org and/or .gov domains, for example: site: .gov, site:, site: .org or restrict to a PDF documen, filetype: pdf

Evaluating Grey Literature

A checklist for evaluating grey literature has been developed by Jess Tyndall, Flinders University.

It uses AACODS (Authority, Accuracy, Coverage, Objectivity, Date and Significance) to evaluate grey literature materials.

  • Authority - Is the author credible?
  • Accuracy -  Is it supported by documented and authoritative references? Is there a clearly stated methodology? Is it in line with other work on the same topic
  • Coverage - Have limitations been imposed and are these stated clearly?
  • Objectivity - Can bias be detected?
  • Date - Can't find the date? Rule of the thumb is to avoid such material
  • Significance - Is it relevant? Would it enrich or have an impact on your research?

For a full version of this checklist please see this document. 

Useful sources