Grey literature is a type of scientific information that is not formally published as articles in scholarly journals. It could be reports, dissertations, manuscripts, clinical guidelines produced by governments, universities and private companies.
An established definition of grey literature (am. gray literature) is as follows:
Joachim Schöpfel. Towards a Prague Definition of Grey Literature. Twelfth International Conference on Grey Literature: Transparency in Grey Literature. Grey Tech Approaches to High Tech Issues. Prague, 6-7 December 2010, Czech Republic. pp.11-26.
Scientific information usually defined as grey literature is for example:
- Conference proceedings
- Unpublished manuscripts
- Recommendations and technical standards
- Government documents
Due to its diverse origins and unpublished nature, grey literature can be difficult to find. It is not, usually, indexed in regularly bibliographic databases.
Where do I find grey literature?
Searching Google is a good start. However, there are specific resources including grey literature, most of them free of charge. Several databases in KIB Finder do also include grey literature; for instance, dissertations are found in Cinahl and PsycInfo.
OpenGrey – European database including around 700,000 references: technical or research reports, doctoral dissertations, conference papers, official publications.
Bielefeld Academic Search Engine (BASE) – One "of the world's most voluminous search engines especially for academic open access web resources", covering around 3,000 resources and more than 60 milllion documents, including several options for limits such as language, publication type and topic.
Health and medicine
Popline, produced by the Johns Hopkins Bloomberg School of Public Health, is a database of eproductive health literature. Besides scientific articles, you'll find unpublished documents in topics like demography, family planning, contraceptives, reproductive health, HIV/AIDS in developing countries and more. In "Advanced Search", you may limit the search to grey literature.
The New York Academy of Medicine is publishing a news letter, The Grey Literature Report in Public Health, alerting readers to new grey literature which are indexed, archived and made available through a search interface. [As of January 2017, the website is no longer updated.]
The Canadian Agency for Drugs and Technologies in Health (CADTH) has developed a comprehensive checklist named Grey Matters. The checklist has an international perspective and do, for example, list the Swedish Agency for Health Technology Assessment (SBU).
To find clinical trials, ClinicalTrials.gov is a good starting point. In addition, International Clinical Trials Registry Platform (ICTRP) by WHO aggregates several trials resources, among them also ClinicalTrials.gov.
DART-Europe – Search engine for European research theses from more than 570 universities in 28 countries.
Dissertations and Theses A&I – Comprehensive and commercial database (ProQuest) for dissertations and theses.