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Using Grey Literature In Literature Reviews: Grey Literature

Grey Literature is included in literature reviews

Examples of Grey literature     What is Grey Literature and why use it? 

It is literature which is produced by all levels of government, academics, business and industry, but which is not controlled by commercial publishers. It can include documents created by government departments, academics, professional bodies, charities, non-governmental organisations, royal colleges, businesses, and industries. Examples include interviews, research reports, blogs, working papers, podcasts, conference proceedings (some published by academic publishers), theses, white papers, policy documents, guidelines, clinical trials, and social media posts. Evidence that almost half of the references in reports on new and emerging nondrug health technologies are grey literature.  

Grey literature can provide current information on emerging areas of research, diverse research perspectives, and studies with null or negative results. It enriches and reduces bias in reviews, making them more inclusive. However, since some grey literature is not peer-reviewed, assessing the quality of the information is essential, as you would for any literature. Newspapers aren’t generally considered grey literature sources because they are "formally published." However, news sources can help assist in the discovery of grey literature.  For example, news items may flag the latest research report or findings, record speeches, and contain statistics and other data.

Searching for Grey Literature

To search for grey literature, we suggest using several diverse sources including online databases, books, library catalogues, websites, and search engines, as no single resource covers all grey literature. Research databases may also include conference papers, theses, and technical reports. The Suggested Grey Literature Resources that are listed in the following text are not exhaustive, as grey literature is continually growing and evolving. 

  • Use broader or multiple combinations of search terms, as search interfaces can be basic. 
  • Develop and adapt a grey literature search plan and keep detailed records of your searches and findings as online content can change.  
  • Use different search engines and not just on Google. 
  • Target relevant think tanks, organizations, agencies, and regulatory or professional bodies, searching their websites or databases individually.  
  • Contact researchers and experts in your field for additional resources. 

 CheckList      Suggested Grey Literature Resources

Below are links to Grey literature resources in many subject areas.

The university subscribes to some Grey literature resources in the A-Z List of Resources. Use the "All Database Types" drop-down menu to filter to the Grey literature heading.

The Grey Literature Non-University Resources list can be filtered by the name or subject area. It can also be downloaded and used in MicroSoft Lists, Excel or CSV formats.. Or you can download this Excel list 

The lists are not exhaustive and there are more ways to search for Grey literature. 

 

 Check Mark     Reporting your Grey Literature

When you report your search on grey literature be sure to include the following information:

  • Name of the website or resource used
  • URL if it is appropriate
  • Date of the search
  • Keywords used for searching or the details of how you browsed

 image of looking glass over documents       Why Use Theses?

Most databases indexing grey literature publications are subject-specific and may not cover all topics. They vary in format, with some resembling bibliographic databases and others using web portal interfaces. We advise you to use theses in a grey literature search because:

  • Some reviews require or expect it 
  • Theses provide additional information on the search topic. 
  • They are often the only source of information on new and emerging topics, reducing potential publication bias.  
  • Theses include unpublished research, essential for comprehensive searches of both published and unpublished original research. 
  • Offer access to international sources like ProQuest Global Dissertations & Theses and Open Access Theses and Dissertations, capturing data from other countries.  

         Tips for finding theses

  • Use Databases that include both published articles and Theses, such as ERIC and PsycInfo, but also consider other sources for a comprehensive search.  
  • Keep your search strategy Simple, as most thesis databases have a basic search interface.  
  • If you are going to do a comprehensive search for all theses on a specific topic, decide on your geographic focus beforehand, whether limited to a specific country or broader, to optimize your searches across multiple sources.  
  • For Thesis, look at  Proquest Dissertation and Thesis and select "Anywhere except Full Text" and Ethos for UK Thesis, then look at the guides above and choose the most appropriate resources for your subject. 

Additional Resources

  • Quick reference guide to get started  
  • Video from Clarivate (who own the WoS) Better searching - truncation, phrase searching and Boolean (5.12) 
  • Need more - Go to Clarivate help page  - scroll down to "Strategies for getting results" and click on + sign to open out page of useful videos. 

Book cover for Bonator Searching the Grey Literature   

Bonato, S. (2018). Searching the grey literature: A handbook for searching reports, working papers, and other unpublished research. Rowman & Littlefield. https://southampton.on.worldcat.org/oclc/1038716407

Book cover of Grey Literature in Library and Information Studies 

Farace D.A. and  Schöpfel J (Eds) (2010) Grey literature in library and information studies.  Berlin; New York: De Gruyter Saur - (available as an e-book) https://southampton.on.worldcat.org/oclc/1334652601

Farrah K, Mierzwinski-Urban M. Almost half of the references in reports on new and emerging nondrug health technologies are grey literature. J Med Libr Assoc. 2019 Jan;107(1):43-48. doi: 10.5195/jmla.2019.539. Epub 2019 Jan 1. PMID: 30598647; PMCID: PMC6300230.

Description: The research investigated how often grey literature is used in reports on new and emerging nondrug health technologies, which sources are most cited, and how grey literature searching is reported. 

GLISC, Grey Literature International Steering Committee Guidelines for the production of scientific and technical reports: how to write and distribute grey literature - Version 1.0., 2006 [Guide/Manual].

Description: To enhance quality and standardization in the production of Grey Literature, members of the Istituto Superiore di Sanità (ISS) in Rome, Italy prepared the first draft of these Guidelines referred to as the "Nancy Style". Adopting organizations are worldwide institutions that produce, process, archive, or distribute grey literature, and which have agreed to implement these guidelines to the degree to which their organization allows.  https://www-ncbi-nlm-nih-gov.soton.idm.oclc.org/nlmcatalog/101273602

Heneghan, C., Perera, R., Badenoch, D., De Brún, C., and N. Pearce-Smith (Eds) (2014). Patient Information: Sources. In Searching Skills Toolkit https://doi-org.soton.idm.oclc.org/10.1002/9781118463093.ch13 

UK Health Security Agency, 2024, Grey literature: index and alternative sources and resources. https://ukhsalibrary.koha-ptfs.co.uk/greylit/      

Description: This list has been compiled to help librarians and researchers, particularly in Public Health, to find resources that fall into this category and flag up alternative sources for queries not easily resolved by the clinical/medical database model. 

Lancaster University Library      https://lancaster.libguides.com/c.php?g=702048&p=5046691

Leeds University library Guide; Grey Literature      https://library.leeds.ac.uk/info/1110/resource_guides/7/grey_literature/2 

Teeside University - Grey Literature: Health        https://libguides.tees.ac.uk/systematic_reviews/searching

University of Waterloo            http://subjectguides.uwaterloo.ca/content.php?pid=94479&sid=4782083 

You can use Google Site Search to search for Grey Literature using domains and countries. The embedded video shows an example of using Google to search for information specific to Zimbabwe on health literacy. The video starts at 31:00 and you can end it at 34:00. (Lancaster University Library. (14 March 2023) Systematic Review Conversations Series: Decolonising of Grey Literature with John Barbrook)   https://youtu.be/eVDYPoDE9Q8?feature=shared&t=1860 

The video demonstrates these steps by typing in the following: 

site:ZW “health literacy” to return articles from Zimbabwe on that topic. 

site:gov.zw “health literacy” to return articles on health literacy from the Zimbabwe government. 

If you want only information in the PDFs returned, add .pdf at the end. 

 site:ZW “health literacy”.pdf 

Please note that there are no spaces after the hyphen following site or the full stop before pdf

 

Examples of using Google Site Search 

The operator is site: followed by the website domain or URL you want to search within and your search term. 

For example, if you want to search for ‘marketing’ on HubSpot’s website, your search query would look like this: 

site:hubspot.com marketing.https://rankmath.com/kb/google-site-search/#:~:text=For%20example%2C%20if%20you%20want%20to%20search%20for%20content%20within,or%20www.konga.com. 

For a single domain, type site: and website URL (no spaces), add a space after URL, type in search term. For multiple sites, type site: and website URL (no spaces) for each website, then add OR between each entry. https://www.lifewire.com/how-to-search-specific-domain-in-google-3481807 

Find more information on getting local search results at https://support.google.com/websearch/thread/2597215/faq-how-to-get-global-local-and-eu-search-results?hl=en.  

The list of country codes https://developers.google.com/custom-search/docs/xml_results_appendices#countryCollections is useful for domain searching.