Finding grey literature
What is grey literature?
Grey literature describes any type of publication that has not been published in the format of a peer reviewed journal article or a book.
It can include reports, preprints, theses, policy documents, working papers, patents, blog posts, clinical trials, data reports, social media posts and more. They can be authored by researchers, businesses, governments, agencies or members of the public.
Benefits of grey literature
Emerging research – Increasingly there is demand for research to be disseminated at a faster speed than traditional journal publishing can facilitate. Preprints and working papers can share immediate results but should be treated as non-peer reviewed material when reading and sharing.
Broad impact – Innovations from the private sector, policy from government and engagement with the public as patients or beneficiaries of research will not generally publish in academic journals and books. Policy documents, industry papers and social media will help you keep up to date with social and economic updates in your field.
Negative and null findings – the scientific replication crisis is fuelled by resistance from some authors and journals to publish null or negative findings. Whilst an increasing number of journals accept these studies; many can be found on repositories and preprint servers.
Finding grey literature
Preprints – keep up with preprint servers in your discipline. A list of popular preprint servers by field is maintained by ASAP Bio.
Theses – doctoral theses from UK institutions are available from the British Library and theses from European institutions at DART Europe. Imperial doctoral theses and some masters theses are available in Spiral.
Policy documents and government reports – policy documents and government reports that are publicly available can often be found using advanced search in internet search engines but results can be difficult to verify. Two specialised policy document databases exist (Overton and Policy Commons), you may need to register for a free account to access.
Clinical trials – databases of privately and publicly funded clinical trials include ClinicalTrials.gov (US and worldwide) and CenterWatch (worldwide). Randomised controlled trials are also searchable in Current Controlled Trials.
Evaluating grey literature
Unlike journal and book content, grey literature has not been peer reviewed. This means you cannot assume that the content is free from bias, error or is up to date. You will have to evaluate the source’s validity yourself.