Grey Literature covers published or unpublished material made directly available from a wide variety of agencies or institutions, often though separate institutional websites. Grey literature includes technical reports, official publications, policy documents, conference papers, dissertations and working papers. Grey literature is usually produced by academic, government and professional organisations. Examples might include the documents of the HSE in Ireland, the NHS in the UK, global agencies such as the World Health Organization. Such documents are usually not indexed in the journal databases such as Medline and Embase.
There is no one search engine that can reliably search multiple websites such as these: often Google or Google Scholar may be the only viable option. Google Scholar for instance is one option for searching grey literature but as it also includes includes all Medline records, it can be time consuming to identify unique healthcare documents.
Often the only viable search option for grey documentation is to extract from all the best studies found any references to documents produced by likely looking agencies. These might be agencies at all levels, national or regional, charities, patient groups, advocacy groups, professional bodies. Conduct a methodical search of all the references and all the citations from the best studies and list the producers. Then search the websites of these sources, the World Health Organization for example. The search engines of many organizations may only handle very basic search statements so a sequence of related searches or page browsing may be necessary.
Recommended grey literature sources are gathered together in this guide, divided into Irish and International Resources but the list of sources is by no means exhaustive.