Grey literature

Find out more about understanding and using grey literature.

Definition and issues

Possibly the hardest thing about grey literature is that it is defined by its absence of qualities rather that its actual properties. The Prague definition is the most recognised definition (Schöpfel, 2010). It is inclusive of virtually all publications but, as highlighted, it is the lack of control by commercial publishers and the resource’s content that it is deemed by the holder to be of a quality to curate.

Effectively it means grey is in the eye of the beholder. Bibliographic control by International Standard Book Number (ISBN) or International Standard Serial Number (ISSN) is not a marker because the definition is based on the motivation of the producer. For example, the Oxford University Press is a commercial publisher so their external publications are unlikely to be considered grey literature. However, a short print run report published, for example, by the University of Liverpool Press, might be issued with an ISBN but still be considered a grey literature publication.

This is further muddied by the question ‘sufficient quality to be collected and preserved by library holdings or institutional repositories’. The curation process determines this, but one person’s sufficient quality is another person’s ephemera. When dealing and handling grey literature is about your own understanding of what it might be and setting your own curation parameters.

Use

Grey literature is often where things develop first, it doesn’t suffer from the inherent time lags a formal publication process engenders. It is the repository of what actually goes on indeed it:

For practitioners it also provides a ready resource of contacts who are working in a given area with whom they may choose to network and obtain expert views from.

Searching for grey literature

When tasked with searching grey literature understanding the nature of the publishers you are handling when looking at literature is key.

It may be useful to think in more practical terms. If it’s about policy or is an organisational report from a government body, quasi-autonomous non-government organization, think tank, charity, public sector body it is likely to fall within the field of grey literature. When you are searching for grey literature bear this in mind and you’ll soon start finding grey literature everywhere, it won’t be labelled as such, and you are constantly making the judgement call.

Limiting retrieval

The sites listed below are best regarded as starters for 10 for limiting retrieval in searches. No one site is totally comprehensive in its coverage of grey literature. Google and other search engines should be used to widen the search. 

To limit the search results think about using:

• phrase searching (for example, “outcomes based commissioning”)
• "site:" (for example, "site:nhs.uk")
• "filetype:" (for example, "filetype:pdf")

Quality

There is generally, but not exclusively, a lack of peer review in grey literature, think tanks can be prone to inherent bias but we should be critically appraising the quality of all materials we handle and advising our users to do likewise. Again, it is about understanding the nature of the producer and producers of both white and grey literature are equally subject to inherent bias’. The key question to ask yourself is, what is this trying to tell me, and why?

Example from practice

The King’s Fund Library Service regularly works with grey literature and provides formal training as well as pointers through our enquiry service on approaches to searching and appraising health and care grey literature materials.

In our training we highlight many of the sources listed below. Approaches to searching for grey literature is often less systematic than searching peer review materials. There isn’t one database which includes all grey literature sources, understanding where, and also, how to use these databases is essential in finding the right information. We consider who produced the work, biases, does it enrich or is it unique research? As well as is it representative of work in that field?

Grey literature is often providing timely information which is useful on topics such as system change like Integrated Care Systems. The work we need to inform cannot wait months or years for articles to be published. Also, not all grey literature form long reports, often we will consider using short briefings or blogs if that is the only information available on a topic. But always mindful of critically appraising and relaying the context to the user.

References

• Henwood, F (2021) Grey Literature Definition for Normal People
• Paez, A (2017) Grey literature: An important resource in systematic reviews in Journal of evidence-based medicine
• Schöpfel, J (2010) Towards a Prague Definition of Grey Literature Paper' presented at the Twelfth International Conference on Grey Literature: Transparency in Grey Literature Grey Tech Approaches to High Tech Issues, Prague

Resources