Grey Literature

  • Learn about grey literature as a research source
  • Build your confidence in finding and evaluating grey literature resources
  • Discover the help and support that is available

Grey literature is defined as "information produced on all levels of government, academics, business and industry in electronic and print formats not controlled by commercial publishing" ie. where publishing is not the primary activity of the producing body." —ICGL Luxembourg definition, 1997. Expanded in New York, 2004.

Why use it?

  • Good resources that help to monitor changes in a particular field
  • Offers the potential to balance any tendencies for publication bias found in published literature.
  • It is a way to locate experts in a field
  • Helps introduce alternative perspectives that may not be represented in standard literature.
  • Is rapidly produced and also very current
  • Information comes from industry and other non-academic institutions
  • Covers current state of affairs and historical collections
  • Is generated on various levels from international, state, province to municipality
  • Includes unpublished research

Examples of grey literature include:

technical or research reports pamphlet speeches
committee reports conference presentations preprint materials
market reports blogs theses and dissertations
conference papers emails newsletters
white papers podcasts clinical trials
poster government documents maps

Who "produces" grey literature?

How to find it?

Select keyword search terms for your topic

  • Choose words that represent the key concepts of your research topic or question

Locate key authors

  • use academic networking
  • use listservs
  • Blogging (blog searching engine)
  • Podcast searching, specialized directories

Create a search string using Boolean operators

  • think of synonyms for each concept and groups synonyms with brackets using OR to connect them
  • use AND operator to search multiple ideas and/or phrases
  • use the truncation symbol * (asterisk) to replace word endings or variant spellings, ie: enviro*
  • use quotation marks to ensure that words are searched together as a phrase

Search strategy

(your topic) AND (meeting* OR abstract* OR poster* OR conference* OR proceeding* OR congress* OR symposi* OR workshop* OR seminar*)

Search strategy example

Start with an OMNI the search engine on the library home page (narrow down results by content type)

Explore the following databases:

Use Cited Reference Searching
Scanning reference lists ‘snowballing,’ bibliographies and academic CVs

Search Repositories

In order to be successful at finding grey literature it is recommended you narrow down the focus of your search. Some things you should think about before beginning your search for grey literature are:

  • What kinds of information are you looking for?
    • theses and dissertations?
    • conference posters, papers, or proceedings?
    • government reports?
    • clinical trials?
  • Who would publish this type of information?
    • government?
    • advocacy groups?
    • academia?
    • industry?
  • Do you have limits to time period or geographic area that you are looking for?

Searching the web

  • Google Scholar 
    • use "advanced search" options to narrow down your search
    •  limit to title
      “Our findings show that GS results contain moderate amounts of grey literature,with the majority found on average at page 80...We recommend that searches of article titles focus on the first 200 to 300 results.”

      Haddaway NR, Collins AM, Coughlin D, Kirk S. The Role of Google Scholar in Evidence Reviews and Its Applicability to Grey Literature Searching. PLoS One. 2015 Sep 17;10(9):e0138237. doi: 10.1371/journal.pone.0138237

  • Google News
  • Google Alerts (set up alerts that cover your topic or follow specific institutions)
  • Google Advanced
    • restricting content to file type 
      • to do this type in your topic and then "filetype:pdf" or "filetype:doc"
    • restricting content to site .org or .gov sites
      • to do this type in your topic and then either "" OR "" 
    • restricting content to searching titles only
      • to do this type search "intitle: "climate change""
    • to exclude words from your search
      • to do this search use operator "-" (minus) eg. jaguar speed -car
    • using Google Australia, Google UK, etc.
    • truncation/wildcard searching is not supported
    • Google & Google Scholar show only the first 1000 results
    • nesting terms in parentheses- eg. (science OR technology) AND (Ontario OR Alberta) - does not work as it does in other databases
  • Use Social media (often organizations and individuals make information about their publications available)
  • Other search engines:


Always evaluate information

  • Authority: Is the author or institution 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 more information explore Evaluating Online Information: Use the CRAP test

How to cite grey literature?

The citation style and the type of document you are working with dictate how you cite it in your work.

Refer to a guide for the particular style you are using (for example, APAChicagoMLA, ...) and follow the format for the type of document you need to cite, for example:

  • technical report
  • web site
  • interview
  • sound recording

Purdue University Online Writing Lab (OWL)

For more information follow Citing your sources

Content last reviewed: October 13, 2020