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Nursing Resource Guide: Grey Literature

About Grey Literature

What is grey literature?

  • Grey literature is defined as "that which is produced on all levels of government, academia, business and industry, in print and electronic formats, but which is not controlled by commercial publishers" Grey Literature Report
  • Grey literature is materials and research produced by organizations outside of the traditional commercial or academic publishing and distribution channels. Common grey literature publication types include reports, working papers, government documents, white papers and evaluations.

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)

More Information on Grey Literature:

Searching for grey literature

There are numerous sources of grey literature including universities, libraries, governments, organizations 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 catalogs e.g. WorldCat

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:


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?

Sources of Grey Literature

American Associations of Colleges of Nursing - The American Association of Colleges of Nursing  is the national voice for baccalaureate and graduate nursing education.

CDC Stacks - CDC Stacks is a free, digital archive of scientific research and literature produced by the Centers for Disease Control and Prevention (CDC). 

Clinical - is a registry and results database of federally and privately supported clinical trials conducted in the United States and around the world.

Centre for Review and Dissemination - This databases provides easy access to quality assessed systematic reviews and economic evaluations and to health technology assessments conducted around the world.

Google Scholar -Google Scholar provides a simple way to broadly search for scholarly literature.

GreyNet International - GreyNet further seeks to identify and distribute information on and about grey literature in networked environments.

Health Research Projects in Progress (HSRProj) - Information about ongoing health services research and public health projects

Kaiser Family Foundation -Kaiser serves as a non-partisan source of facts, information, and analysis for policymakers, the media, the health care community, and the public.

LILACS - LILACS, from the Latin American and Carribben Center on Health Information, is the most important and comprehensive index of scientific and technical literature of Latin America and the Caribbean.

Latin American Open Archives Portal(LAOAP) - The Latin American Open Archives Portal (LAOAP) is a project to build a scholars’ portal at the Latin American Network Information Center (LANIC) to improve access to social sciences grey literature produced in Latin America.

Mednar - Mednar is a free, publicly available deep web search engine that uses advanced federated search technology to return high quality results by submitting your search query - in real-time - to other well respected search engines. Mednar then collates, ranks and drops duplicates of the results.

medRxiv - medRxiv (pronounced "med-archive") is a free online archive and distribution server for complete but unpublished manuscripts (preprints) in the medical, clinical, and related health sciences. Preprints are preliminary reports of work that have not been peer-reviewed. They should not be relied on to guide clinical practice or health-related behavior and should not be reported in news media as established information.

New York Academy of Medicine Grey Literature - A bimonthly publication of The New York Academy of Medicine Library alerting readers to new grey literature publications in health services research and selected public health topics. In addition to this alert service, all resources are added and indexed in our Online Catalog.

National Information Center on Health Services Research and Health Care Technology (NICHSR) - HSR Information Central is not an index of all health services resources on the Web. Rather, it contains selective links representing a sample of available information. Items are selected for their quality, authority of authorship, uniqueness, and appropriateness.

National Library of Medicine Locator Plus - Generally doesn’t provide full text access to documents, but a good way to see what sort of government reports exists on a topic.

National Guidelines Clearinghouse ARHQ - This is a public resource for evidence-based clinical practice guidelines.

National Research Registry - Guide to research sponsored by, or of interest to Great Britain’s National Health Service.

NTIS - The National Technical Information Service serves as the largest central resource for government-funded scientific, technical, engineering, and business related information available today.

OpenDOAR - an authoritative directory of academic open access repositories.

OpenSIGLE (OpenGrey) - System for Information on Grey Literature in Europe.

Partners in Information Access for Public Health Workforce - Good collection of links to Grey Literature resources in Public Health including newspapers, reports and guidelines.

Robert Wood Johnson Foundation (publications & research) - The mission of the Robert Wood Johnson Foundation is to improve the health and health care of all Americans.

Virginia Henderson Global Nursing e-Respository - offer nurses, in all roles around the globe, online access to reliable nursing information that can be easily utilized and shared.

World Wide - is a global science gateway comprised of national and international scientific databases and portals.

World Health Organization Current Bibliography - Catalogs of publications by the World Health Organization and affiliated agencies including technical and policy documents.

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 catalog using the complete conference title or the location and year. If not successful try searching WorldCat.

Google - many societies and organizations 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:

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


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