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Qualitative Research: Grey Literature

What is Grey Literature?

Grey literature is generally material not published commercially or indexed by major databases. 

A more complete definition is information "produced on all levels of government, academics, business and industry in electronic and print formats not controlled by commercial publishing i.e. where publishing is not the primary activity of the producing body." (

Based on University Libraries, University Washington

What Does Grey Literature Include?

Reports, preprints, working documents, research papers, theses and dissertations, clinical trials,  bibliographies, newsletters, patents, statistical documents, white papers, pamphlets, informal communication (e.g., blogs, podcasts, email), and more.

Invisible Web

(Only SOME of the Invisible Web [grey box] material is available via Pacific Universities Libraries databases and sites listed on this guide.)

Data from P. Gil, "What is the invisible web?" Dec. 2010. Schematic by N. Tann, Goshen College, March 2011.

Image: The Harold & Wilma Good Library

Sources of Grey Literature

  • Deep Web Searching
  • Institutional Repositories
  • Reports and Research, Theses/Dissertations, Clinical Trials

Deep Web

The Deep Web, also known as the Invisible Web, is a portion of the web not reached by standard search engines, such as Google and Bing. Less than 10% of the web is indexed by search engines, with the remaining 90% of web content called the Deep Web. It is estimated to be 2-500x bigger than the visible web. 

Here are some general resources to search the Deep Web:

Institutional Repositories (CommonKnowledge)

An Institutional Repository is a virtual space where a university or research institute collects and preserves its research and findings. Information in Repositories is considered grey literature since these resources are not traditionally published.

  • CommonKnowledge at Pacific University: digital repository of articles, technical reports, dissertations, datasets, images and other file types produced at Pacific University by faculty, researchers, and students.
  • CommonKnowledge - search ALL institutional repositories - change searching to ALL repositories
  • OpenDOAR: directory of open access repositories

Reports, Theses/Dissertations, Clinical Trials

Reports and Research:


Clinical Trials

  • CenterWatch : Global source for clinical trials information, offering news, analysis, study grants, career opportunities, and trial listings to professionals and patients
  • Registry and results database of federally and privately supported clinical trials conducted in the United States and around the world
  • EU Clinical Trials Register:  Registered clinical trials in the European Union 
  • ISRCTN Register: Registered randomized controlled trials and other studies to assess the efficacy of health care interventions around the world  

Additional Grey Literature Resources