"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"  -ICGL Luxembourg definition, 1997- Expanded in New York, 2004

"Gray literature...refers to informally published written material (such as reports) that may be difficult to trace via conventional channels such as published journals and monographs because it is not published commercially or is not widely accessible." - Wikipedia definition of "grey/gray literature"

Source: http://www.slideshare.net/giustinid/libr534-class-vi-ib2

"Grey literature may not stand alone, but it can contribute substantively to understanding scientific challenges. [In scientific research] every source should be considered in the exploration of an issue. In some domains, the best source of information may be grey. Some grey literature goes through as stringent (or more) of a review as commercially published content." -Richard Huffine, National Library Coordinator, USGS

Finding grey literature can be difficult and require exhaustive searching. Since grey literature is not included in bibliographic databases, it requires different search techniques in order to find information relevent to your topic of interest. The links below offer quick introductions and tutorials, but a librarian is always a great place to start!
 

• Finding the hard to finds: searching for the grey literature in biomedicine.
  A PowerPoint presentation on how to find grey literature, created by Dean Giustini,
  Biomedical Librarian at The University of British Columbia

Google Advanced Search or Google Scholar Advanced Search - Use advanced search to improve precision. Access advanced search in Google Scholar from the menu in the top left of the page.Try date limits or domain limits (.org or .gov) to narrow results. You can also use Google Advanced Search to search a specific web site (bottom of advanced search page). Google is also a good way search for conference proceedings and meetings, ex.: concussions conferences. 

Organizations

Organizations are also a good method for finding grey literature. Identify organizations that are likely to create publications in your area of research, such as:

• government agencies
• advocacy groups and private agencies
• industry, trade or professional organizations

Once you have identified an organization of interest, you can generally locate publications on their Web site.

Organization Publishers from the Grey Literature Report: This is a list of hundreds of publishers and organizations that produce grey literature.

MedlinePlus Organizations: A  List of health information organizations, including government agencies, foundations, professional societies, research associations, and disease support groups.

Health Services Research Information Center:

• HSRProj: Health Services Research Projects in progress provides access to information about current research-in-progress before results are available in published form. Contains over 15,000 active reports.
• HSRR: Health Services/Sciences Research Resources is a searchable database of information about research datasets and instruments/indices employed in Health Services Research, and the Behavioral and Social Sciences.
• HSRIC: Health Services Research Information Central is a research portal of health services research resources providing numerous Internet links to data, funding announcements, reports, podcasts, discussion groups, and more.
• PHPartners: Partners in Information Access for the Public Health Workforce is a collaboration of U.S. government agencies, public health organizations and health sciences libraries whose mission is helping the public health workforce find and use information effectively to improve and protect the public's health. The site includes public health topics from bioterrorism to obesity and nutrition along with public health data and statistics, grants and funding announcements,legislative & policy links, and conferences and meetings focusing on public health.

The Health and Medicine Division (HMD) Reports - The Health and Medicine Division (HMD) of the National Academies (formerly Institute of Medicine, IOM) publish reports that provide objective and straightforward advice to decision makers and the public. This site includes reports published after 1998.

​Agency for Healthcare Research & Quality (AHRQ) - AHRQ provides data on the cost and use of health care, scientific information on health care and results of medical treatments, as well as data on special needs of priority populations.             

BMC Proceedings

BMC Proceedings is an online, open access journal publishing proceedings of conferences across all scientific and clinical disciplines, including peer-reviewed full-length articles, collections of abstracts and meeting reports.

• CDC Stacks
  CDC Stacks is a free, digital archive of scientific research and literature produced by the Centers for Disease Control and Prevention (CDC). This online archive is composed of curated collections tailord for public health research needs.
                    
• Centre for Review & Disseminations (CRD)
  Provide research-based information about the effects of health and social care interventions via CRD databases and undertake systematic reviews evaluating the research evidence on health and public health questions of national and international importance

• NASA Technical Reports Server

The NTRS provides access to NASA's current and historical technical literature and engineering results. Over 500,000 aerospace-related citations, over 200,000 full-tect online documents and over 500,000 images and videos are available.

• National Center for Health Statistics (NCHS) (CDC)
  The NCHS' website is a rich source of information about America's health. The site provides a wide range of data from birth/death records, medical records, interview surveys to direct physical exams and laboratory testing.

• NIH RePORT Searchable Public Databases
  A directory of searchable public databases provided by the National Institute of Health (NIH). Links to RePORTER, NIDB Resources, NCBI Literature Databases, PubMedCentral, PubMed (Medline), Research.gov, Community of Science, Science.gov, World Wide Science and ClinicalTrials.gov are available.
   
• OAIster
  OAIster is a union catalog of millions of records representing open access resources that was built by harvesting from open access collections worldwide using the Open Archives Initiative Protocol for Metadata Harvesting (OAI-PMH). OAIster includes more than 25 million records representing digital resources from more that 1,100 contributors.

• OpenDOAR

Directory of Open Access Repositories

• OpenSIGLE (OpenGrey)
  System for Information on Grey Literature in Europe, is your open access to 700,000 bibliographical references of grey literature (paper) produced in Europe and allows you to export records and locate the documents. 

• Public Health Image Library (PHIL)
  From the Centers for Disease Control and Prevention, the Public Health Image Library (PHIL) provides access to photographs, illustrations and multimedia files relevant to public health and health care.
   
• Public Health Partners
  Helping the public health workforce find and use information effectively to improve and protect the public's health.
   
• Science.gov
  Science.gov searches over 55 databases and over 2,100 selected websites from 13 federal agencies, offering 200 million pages of authoritative U.S. government science information including research and development results. Science.gov is governed by the interagency Science.gov Alliance.
   

• TRIP Database
  Trip is a clinical search engine designed to allow users to quickly and easily find and use high-quality research evidence to support their practice and/or care. Includes images, videos, patient information leaflets, educational courses and news. 
   
• United Nations Official Documents System
  ODS provides access to the resolutions of the General Assembly, Security Council, Economic and Social Council, and Trusteeship Council from 1946 onwards. ODS includes pre-session, in-session and post-session documentation ofr the General Assembly and its subsidiary bodies; the Security Council and its subsidiary bodies; the Economic and Social Council and its subsidiary bodies; and the Trusteeship Council; and for global conferences convened by the UN, as well as for meetings included in the Calendar of Conferences and Meetings authorized by the General Assembly.
   
• U.S. Food & Drug Administrtaion (FDA)
  FDA for Science & Research provides access to clinical trials, product development, and R&D.
   
• USAID Development Experience Clearinghouse
  Search a half-century of U.S. international aid records. Use advanced search to narrow your results.
   
• Virtual Health Library
  A repository of scientific information and knowledge focused on South America and the Caribbean, supported by BIREME, PAHO, & WHO.

Read more about Web of Science Conference Proceedings selection process

• ClinicalTrials.gov
  Provides information on U.S. government & privately funded clinical trials, including trials no longer recruiting patients.
   
• Cochrane Central Register of Controlled Trials
  Subscription database available through KUMC that provides high-quality research and access to clinical trials.

•  IRSCTN Registry - BioMed Central Current Controlled Trials
  Search across multiple trial registers.

• OpenTrials

It aims to locate, match, and share all publicly accessible data and documents, on all trails conducted, on all medicines and other treatments, globally.

• Health Services Research Projects in Progress (HSRProj)  Coordinated by the National Information Center on Health Sciences Research and Health Care Technology

• IFPMA Clinical Trials Portal
  From the International Federation of Pharmaceutical Manufacturers & Associations (IFPMA), a global non-profit NGO representing the research-based pharmaceutical, biotech, & vaccine sectors.

• GSK Clinical Study Register  Provides data from clinical studies sponsored by Glaxo-Smith-Kline.

• WHO International Clinical Trials Registry Platform

• E.U. Clinical Trials Register
  Information about clinical trials in the E.U. from the confidential, E.U. clinical trial database.