Skip to Main Content
It looks like you're using Internet Explorer 11 or older. This website works best with modern browsers such as the latest versions of Chrome, Firefox, Safari, and Edge. If you continue with this browser, you may see unexpected results.

Grey Literature in Research

Provide information and updated resources to search and include grey literature in research

Introduction to Grey Literature

Welcome to the Grey Literature in Research LibGuide!  Grey literature has always existed, but the term itself was not coined until the mid 1970’s. Since its coined induction it has taken on several definitions. All changing and adapting to how we communicate and share information. As of today grey literature is defined as "Information produced on all levels of government, academia, 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".

Types of Grey Literature

The expansion of how we communicate and disseminate information has significantly impacted how we define source materials as grey literature. Over the last two decades different variations of grey literature sources have been established. There are over 20 different types. The most commonly used are listed below. For an extensive list of types check out GreyNet International.


Blogs E-mail Discussions Lists Pamphlets Statistical Reports
Clinical Trials Government Documents/Reports Patents Survey Results
Conference Papers Interviews Policy Statements Tweets
Discussion Forums Market Reports Pre-prints Videos
Dissertations/Thesis Newsletters Research Reports Wikis

TIP: Citating grey literature may seem like a daunting task. According to the APA (7th ed.) , format citations and references in book format for grey literature material. For additional help on formatting non-traditional resources click here

Datebases and additional resources to search Grey Literature

BMC Proceedings
F1000 Posters: The Open Poster Repository
Web of Science
IEEE Xplore
Subjects covered include aerospace, biomedical technology, computer science, computing and control technology, consumer and industrial electronics, electrical and electronics engineering, information systems, power, robotics, telecommunications. To limit search to full text available to Pollak Library, select 'Search subscribed full-text content only' under the Publications heading on the IEEE search page.
Search conference proceedings from nearly 50 disciplines and hundreds of conferences. Sort by discipline or use a keyword search.

A registry and results database of publicly and privately supported clinical studies of human participants conducted around the world.

Cochrane Central Register of Controlled Trials

A bibliographic database that provides a highly concentrated source of reports of randomized controlled trials. Note that they do not contain the full text of the article.

Eli Lilly Clinical Trial Registry

Information about clinical trials and observational / non-interventional studies sponsored by Eli Lilly & Company.

European Union Clinical Trials Register

Search for protocol and results information on: interventional clinical trials that are conducted in the European Union (EU) and the European Economic Area (EEA) as well as clinical trials conducted outside the EU / EEA that are linked to European paediatric-medicine development.

GlaxoSmithKline (GSK) Clinical Study Register

Provides an easily accessible repository of data from GSK-Sponsored Clinical Studies, supplementing communication in journals, at scientific meetings, in letters to healthcare professionals, and in approved prescribing information.

Health Services Research Projects in Progress (HSRProj)

Information about ongoing health services research and public health projects.

ISRCTN Registry

The ISRCTN registry is a primary clinical trial registry recognized by WHO and the International Committee of Medical Journal Editors (ICMJE) that accepts all clinical research studies (whether proposed, ongoing or completed), providing content validation and curation and the unique identification number necessary for publication. All study records in the database are freely accessible and searchable.

National Registry of Evidence-based Programs and Practices (NREPP)

Substance Abuse and Mental Health Services Administration’s (SAHMSA) National Registry of Evidence-based Programs and Practices (NREPP) promotes the adoption of scientifically established behavioral health interventions.


The NIH Research Portfolio Online Reporting Tools provides access to reports, data, and analyses of NIH research activities, including information on NIH expenditures and the results of NIH supported research.


PROSPERO is an international database of prospectively registered systematic reviews in health and social care. PROSPERO aims to provide a comprehensive listing of systematic reviews registered at inception to help avoid unplanned duplication and enable comparison of reported review methods with what was planned in the protocol.

Trials Register of Promoting Health Interventions (TRoPHI)

Covers trials of interventions in health promotion and public health worldwide, including both randomized and non-randomized controlled trials.

WHO International Clinical Trials Registry Platform (ICTRP)

Contains the trial registration data sets from the following registries: Australian New Zealand Clinical Trials Registry, Chinese Clinical Trial Registry, EU Clinical Trials Register, ISRCTN, and Netherlands National Trial Register.

EthOS (Electronic Theses Online Service)

EThOS is the UK’s national thesis service which aims to maximise the visibility and availability of the UK’s doctoral research theses.
It demonstrates the quality of UK research, and supports the UK Government’s open access principle that publications resulting from publicly-funded research should be made freely available for all researchers, providing opportunities for further research.

Networked Digital Library of Theses and Dissertations
ProQuest Dissertations & Theses (PQDT) Global is the world's most comprehensive collection of dissertations and theses from around the world, offering millions of works from thousands of universities. Each year hundreds of thousands of works are added. Full-text coverage spans from 1743 to the present, with citation coverage dating back to 1637.



Catalog of U.S. Government Publications

The CGP is the finding tool for federal publications that includes descriptive information for historical and current publications as well as direct links to the full document, when available.

Data Gov

An online repository of policies, tools, case studies, and other resources to support data governance, management, exchange, and use throughout the federal government

Electronic Code of Federal Regulations

Federal Registrar

The Office of the Federal Register (OFR) of the National Archives and Records Administration (NARA), and the U.S. Government Publishing Office (GPO) jointly administer the website. The  website was developed to make it easier for citizens and communities to understand the regulatory process and to participate in Government decision-making.



HathiTrust is a partnership of academic and research institutions, offering a collection of millions of titles digitized from libraries around the world. HathiTrust contains a collection of U.S. Federal Documents via the HathiTrust Federal Government Documents Registry. This collection is a work in progress, and is updated regularly to add and remove content.

Directory of Open Access Journals (DOAJ)
Grey Literature Report


OpenGrey, System for Information on Grey Literature in Europe, is your open access to 1 014 872 bibliographical references of grey literature (paper) produced in Europe and allows you to export records and locate the documents. Examples of grey (gray) literature include technical or research reports, doctoral dissertations, some conference papers, some official publications, and other types of grey literature. OpenGrey covers Science, Technology, Biomedical Science, Economics, Social Science and Humanities.

PAIS International

This resource covers issues in the public debate through selective coverage of a wide variety of international sources including journal articles, books, government documents, statistical directories, grey literature, research reports, conference papers, web content, and more. PAIS International is the current file covering 1972 to present, and PAIS Archive includes the content from printed volumes published 1915-1976.

United Nations Official Document System

The Official Document System (ODS) is an online database of UN documents that was first launched in 1993 and updated in 2016. ODS has full-text, born-digital UN documents published from 1993 onward, including documents of the Security Council, the General Assembly, the Economic and Social Council and their subsidiaries, as well as administrative issuances and other documents.

Using Google to search Grey Literature

 If you are not sure which direction to go in when starting a search, google can be used as a viable source. Understanding how to use google operators will increase your chances of finding on-point and valuable information related to your topic. Listed below in the table are a few google search operators that are commonly used when starting a search.

Operator Description Example
OR (I) Search one or all terms and phrases

Grey Literature OR Gray Literature

Grey Literature (I) Gray Literature

AND  Search all terms and phrases Grey Literature AND Gray Literature
- Excludes term or phrase Grey -Literature
(....) Allows multiple operators and phrases to be searched together (grey literature OR gray literature) academic
"......" Blocks synonyms and searches exact phrase/term "Grey Literature"
related: Find sites related to domain of choice related:

TIP: Google routinely updates and adds to its search operators to improve usability. Search operators may be discontinued or become default or automatic controls for google searches.

Evaluating Quality of Sources

Using grey literature in your research can be a useful resource, but it is important to determine the quality of the grey literature you are using.  The reasons being:

  • Grey literature may not have went through the same rigorous process as peer reviewed content.
  • Important citation information may be missing or completely absence, making it hard to determine source origin and credibility.
  • Some sources of information may be bias because the content was funded for profit.

AACODS Checklist

Evaluting the quality of grey literature can be complex. The AACODS checklist assists with creating a standard for evaluting and critically appraising grey literature content. AACODS is based off of five determining principles: Accuracy, Authority, Coverage, Objectivity. Date, and Significance.

For more information about  AACODS Checklist review here.

CADTH Checklist

The Canadian Agency for Drugs and Technologies in Health developed a practical tool for searching health-related grey literature. The tool contains a grey literature checklist. The checklist is broken into several sections covering areas like national and international health technology assessment websites (HTA), drug and device regulatory approvals, clinical trial registries, health economic resources,and  drug formulary websites.

For more information about the CADTH Checklist review here.