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Unit 5: Systematic reviewing - Finding grey literature

Grey literature is information like theses, reports, conference proceedings, clinical trials, policy documents or guidelines. This can be produced by a wide variety of sources such as national or local government, charities, or academics. It can be hard to find as it may not be indexed in the main databases and sources. This page outlines the main sources in health, but you should always consult your library subject guide for other useful sources.

Clinical trials

  • The National Institute for Health Research (formerly the National Research Register) covers research carried out in England and has a searchable archive which covers UK wide older research
  • ClinicalTrials.gov produced by the US National Library of Health. This indexes trials in the US and worldwide.
  • CenterWatch as a searchable database of listings of worldwide industry and government-sponsored clinical trials. Sponsors use this service to inform patients and their caregivers about ongoing clinical trial opportunities, which volunteers can then review and inquire about participating in.
  • Current Controlled Trials allows users to search, register and share information about randomised controlled trials. Access to all the information on this site is free.
  • Trials is an open access, peer-reviewed, online journal from BioMed Central that covers the performance and findings of randomized controlled trials.

Search engines

You can find a lot of useful information on the internet, but it can be hard to focus your search and to judge the quality of what you find. Some have an advanced search which helps filter your search results. Look for specialist search engines such as Google Scholar, which searches academic publications.

Here are some general tips to help you use search engines:

  • use the advanced search option
  • don’t use truncation
  • AND is the default which means that the words you type must all be mentioned, link synonyms using OR
  • specify the domains gov, ac or org
  • limits:
    • exact phrase (don’t use truncation)
    • with at least one of the words
    • in the title of the article

Creative Commons License
SMILE - Systematic Reviewing by Dr Helen Marlborough, Glasgow University and Marion Kelt, Glasgow Caledonian University is licensed under a Creative Commons Attribution 3.0 Unported License