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Research Tips: Grey Literature

Research tips, support, strategies and FAQs

About Grey Literature

What is grey literature?

Grey literature is defined as "multiple document types produced on all levels of government, academics, business, and organization in electronic and print formats not controlled by commercial publishers i.e. where publishing is not the primary activity of the producing body." GreyNet.

In effect this means that most grey literature will not be searchable or accessible via conventional databases.

Why include grey literature in your review?

  • Can address publication bias - "a recently updated Cochrane methodology review---showed that published trials showed an overall greater treatment effect than grey literature trials (Hopewell 2007)"   
  • May be the only source of some data - "conference abstracts and other grey literature have been shown to be sources of approximately 10% of the studies referenced in Cochrane reviews (Mallett 2002)"  Cochrane Handbook for Systematic Reviews of Interventions                                                                           

Grey literature includes:

  • conference papers / proceedings
  • theses
  • clinical trials
  • reports
  • research data
  • working papers
  • practice guidelines
  • government documents
  • fact sheets / bulletins
  • newsletters
  • pamphlets
  • surveys / interviews
  • informal communication (e.g. blogs)

 

Searching for grey literature

There are numerous sources of grey literature including universities, libraries, governments, organisations and websites. See the adjacent box 'Sources of Grey Literature' for  websites / databases designed to mine grey literature in specific fields. Also search large library catalogues e.g. WorldCat or the the National Library of Australia's Trove.

Web Search Tips

  • You may need to employ different search strategies for different websites.
  • Look for the Help link on the website to see if it supports Boolean operators AND, OR, NOT; (brackets) for order of operations; wildcard ? for single letter; truncation * for different endings; "exact phrase" searching. The table below explains how Boolean operators work.

         

  • If your search retrieves too many generalised / irrelevant results add another relevant concept with AND.
  • If your search retrieves too few results remove a concept / keyword.
  • If you receive no results check your spelling / include alternative spelling e.g. grey OR gray
  • You can focus a Google / Google Scholar search by including one of the following limits - site:org  site:gov  filetype:pdf

"in recent years it has become clear that the likelihood of finding a critical unpublished study or study data that changes key summary outcomes may be greater than we had once thought. For this reason, we are recommending searching these other sources for studies that might otherwise not be identified... we temper our recommendation for searching other sources with a recommendation to be selective and to choose the sources to be searched where it makes most sense." (Balshem, H. et al. 2013. Reference below)

Evaluating grey literature

As with all evidence, it is important to appraise grey literature and ascertain its quality / relevance. A critical appraisal checklist for grey literature was developed by Jess Tyndall, Flinders University in 2010:

AACODS

Authority - is the author credible / reputable?

Accuracy - is there a clearly stated aim & methodology which has been met? Supported by authoritative references / sources? Is it representative of other work in the field / provides a valid counterbalance?

Coverage - are any limits clearly stated?

Objectivity - any obvious bias?

Date - does the date relate to the content? Can't find the date? Be very wary.

Significance - is it relevant? Does it enrich / impact on your research?

 

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Grey Literature Search Tools

How to find conference proceedings / papers / posters

The collection of papers / posters presented at a conference are know as conference proceedings. These may be published in book format, as special issues of a journal, or as a serial.

Conference proceedings are often difficult to find. You may be able to find them by searching a relevant library catalogue using the complete conference title or the location and year. If not successful try searching WorldCat.

Google - many societies and organisations publish their proceedings on their website. You can also try searching for the title as a "phrase" (using quotation marks).

The following databases may also have conference papers on your topic:

Embase

  • Complete a search
  • Additional Limits > Publication Types > 'Conference Abstract', 'Conference Paper', 'Conference Proceedings' and 'Conference Review'

MEDLINE

  • Complete a search
  • Additional Limits > Publication Types > 'Congresses', 'Clinical Conference' and 'Consensus Development Conference'
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