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Gray Literature

This guide will describe what gray literature is and how to find useful resources for your research.

What Is Gray Literature?

Gray literature is a concept that refers to a wide variety of unpublished or informally published information from different groups such as professional associations, research institutes, government agencies, and non-profit organizations. It is usually difficult to track down this type of information because it is not published commercially (e.g. in a research journal), nor is it widely accessible.

For a more in-depth discussion of the definition of gray literature, please see "Toward a Prague Definition of Grey Literature" by Joachim Schoepfel, specifically page 18.

Who Uses Gray Literature?

  • Researchers
  • Practitioners
  • Policymakers
  • Students

Types of Gray Literature

Gray literature comes in many different forms. Some examples include:

  • Abstracts
  • Reports
  • Newsletters
  • Preprints
  • Journal supplements
  • Working documents
  • Theses & dissertations
  • Clinical trials
  • Bibliographies
  • Book chapters
  • Statistical documents
  • White papers
  • Conference proceedings
  • Information communication (e.g. blogs, email, etc.)

Why Use Gray Literature?

Although it may be difficult to find, gray literature can be an important part of your research because it:

  • Provides a very current perspective
  • Fills in gaps present in the published literature
  • Helps overcome a positive publication bias present in some of the published literature
  • Compensates for a time-lag bias in the published literature
  • May help provide a more international perspective

Potential Weaknesses

Like all information, gray literature has some potential weaknesses to be aware of:

  • Lack of peer review
  • Possibly less reliable / questionable quality
  • Written for a purpose that may not be scientific (e.g. to promote a product)
  • Potentially short information life cycle
  • Document types can be very different, making it difficult to compare
  • Searching may involve considerable time, effort and expense
  • Access to full text or complete data may be a challenge
  • Finding/indexing tools may not be readily available