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Systematic Reviews

What is Grey Literature?

Grey literature is “information produced  by all levels of government, academics, business and industry in electronic and print formats not controlled by commercial publishing”. (GreyNet)


Grey literature includes:

Theses and dissertations, conference proceedings, newsletters, reports, government documents, informal communications, translations, census data, research reports, technical reports, standards, patents, videos, clinical trials and practice guidelines, eprints, preprints, wiki articles, emails, blogs, listserv archives, repository content.


Grey literature may present a number of challenges for the researcher:

  • Difficult to find
  • Many documents are not published online
  • Older documents may not be archived
  • Short print runs may lead to lack of availability
  • Format and citation information may be inconsistent
  • Volume of material may be over-whelming and time-consuming
  • Quality of evidence varies.

Clinical Trials Registers

Also check the lists included in Cochrane Handbook for Systematic Reviews of Interventions (Section 4.3.3 Trials registers and trials results registers)

Conference presentations



What is included?

How to search


Scopus includes most of the content from Embase, which contains almost 800 conferences and more than 260,000 conference abstracts, primarily from journals and journal supplements published from 2009.

Limit by "Document Type":

Conference paper
Conference review

MEDLINE Includes some citations to individual poster/paper abstracts – may include abstracts. Journal supplements often not included. Limit by "Publication Type":

Clinical conference
or use the MESH heading "Congresses as topic"

Web of Science Includes "Conference Proceedings Citation Index - Science" and "Conference Proceedings Citation Index - Social Science & Humanities". Rarely includes abstract.

Limit by "Document Type":

Meeting abstracts
Proceedings papers

HSRProj (Health Services Research Projects in Progress) Information about ongoing health services research and public health projects from the US National Institutes of Health. From 12 September 2021, this database is not being maintained. Access the information directly from the funders listed on this page.  

Databases indexing grey literature



Type of grey literature

Analysis & Policy Observatory

Public policy research reports, articles and data from academic research centres, think tanks, government and non-government organisations. Also features opinion and commentary pieces, video, audio and web resources particularly for issues facing Australia and New Zealand.

Google Scholar

Articles, theses, books, abstracts and court opinions, from academic publishers, professional societies, online repositories, universities and other web sites.

International HTA Database Bibliographic information about ongoing and published health technology assessments commissioned or undertaken by HTA organisations from around the world. A valuable source for identifying grey literature as much of the information it contains is only available directly from individual funding agencies.
MedNar One-stop search across medical societies, NIH resources, other U.S. government websites, and patents.
OAlster Catalog of millions of records representing open access resources from open access collections worldwide. OAIster includes more than 25 million records representing digital resources from more than 1,100 contributors.
OpenDOAR Global directory of academic open access repositories containing full-text resources.
Open Grey Open access to 700.000 bibliographical references of grey literature (paper) produced in Europe and allows you to export records and locate the documents. Gateway to over 50 million pages of authoritative selected science information provided by U.S. government agencies, including research and development results Global science gateway-accelerating scientific discovery and progress through a multilateral partnership to enable federated searching of national and international scientific databases.

Finding theses

Once you know the details of a thesis, how do you obtain the thesis? Here is a summary of what to do:

Web Searching