When writing a paper or preparing an assignment, we usually start with journals and books. Yet there is an enormous number of documents that rarely show up in bookstores or journal indexes, such as research reports from government ministries, technical documents released by companies, graduate theses, and materials presented at academic conferences. The name that groups all of these materials together is “grey literature.”
Simply put, grey literature refers to materials produced and released directly by institutions such as governments, universities, companies, and civic organizations, without passing through commercial publishers or the distribution channels of formal academic publishing. The content is often rich, but it is hard to find and uneven in quality, which makes it a persistent challenge for libraries and researchers.
In this article, we will look in turn at how the term grey literature came about and how it is defined, the main types of material, why it matters in research, and the problems of finding and preserving it along with the efforts to solve them.
Knowledge Beyond the Boundaries of Publishing
How the Name “Grey” Came About
The term grey literature came into wide use in the 1970s. Behind it lay the enormous volume of reports produced during the Second World War.
(1) Auger and Reports Literature
In 1975 the researcher Charles P. Auger published Use of Reports Literature, which dealt with intelligence reports produced by the Allies during the war and records of atomic energy research. He is said to have first used the term at a 1978 meeting held by the British Library Lending Division.
(2) Semi-Published Material
Auger acknowledged that reports had advantages over journals: they were faster and more flexible, and could include very detailed content when needed. At the same time, he pointed out that because they were in a “semi-published” state, neither published nor unpublished, they were hard for librarians to collect and organize.
(3) The Luxembourg Definition
The Third International Conference on Grey Literature in 1997 defined grey literature as material produced on all levels of government, academics, business and industry in print and electronic formats, but not controlled by commercial publishers. In 2004, the explanation was added that it is material produced by organizations whose primary activity is not publishing.
What Counts as Grey Literature?
Grey literature is not a single format but a name for a very wide variety of materials. The main types are as follows.
- Research Report: a report of results issued by a government-funded research institute or agency after completing a research project.
- Thesis and Dissertation: papers written in master’s and doctoral programs, often containing much that never appears in journals.
- Conference Proceedings: collections of papers and presentation materials delivered at academic conferences.
- Working Paper: a research manuscript released early to gather feedback before formal publication.
- Government Publication: documents issued by public bodies, such as white papers, statistics, and policy evaluations.
Technical standards, patents, annual reports, newsletters, and lecture materials also count as grey literature. Records such as handwritten manuscripts and personal letters, on the other hand, are usually classified separately.
Why Grey Literature Matters in Research
You might think journals alone would be enough, but in many fields grey literature is indispensable evidence.
(1) Faster and More Detailed Information
Research results often appear first as reports, theses, or conference materials, and it can take 12 to 18 months before they are formally published elsewhere. With fewer length limits, they also commonly describe experimental procedures and data in more detail than journals do.
(2) Reducing Publication Bias
Results showing that something works are readily published in journals, while results showing no effect are easily buried. That is why systematic reviews in health and medicine search for and analyze grey literature as well, to avoid this publication bias.
(3) Different Weight in Different Fields
In fields with many field reports, such as agriculture, aeronautics, and engineering, grey literature can even be the main source. In archaeology, too, site surveys and excavation reports often circulate as grey literature.
Hard to Find and Easy to Lose
The biggest weakness of grey literature is poor bibliographic control. Quite often even basic information such as the author, date of publication, or issuing organization is missing.
(1) Changes Brought by the Internet
From the late 1990s, as governments, universities, and companies began posting reports online, grey literature became far easier to obtain. But as the amount of material exploded, picking out what is trustworthy became harder instead.
(2) Vanishing Addresses
Many documents never receive a stable address or a digital object identifier (DOI), so over time links break and cited materials can no longer be found.
(3) Efforts to Collect and Preserve
GreyNet has held the International Conference on Grey Literature since 1993, and in 2014 the Pisa Declaration on Policy Development for Grey Literature Resources was issued. arXiv, which collects preprints in physics and other fields, and RePEc, which collects economics working papers, are leading repositories that gather grey literature.
Grey literature is easily overlooked because it lies outside the boundaries of formal publishing, yet it is full of research results that never made it into journals and vivid records from the field. Because it is hard to find and uneven in quality, the ability to judge where and how to find it and how far to trust it becomes all the more important.
Gathering scattered reports and papers, organizing them, and keeping them for the long term: that is the first step of library and information science in connecting us to hidden knowledge.
