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Advanced literature search and systematic reviews

An introduction to systematic reviews

Grey literature

To carry out a thorough search of the literature, you should also identify grey literature, work that is either unpublished or has been published in non-commercial form. Grey literature is produced by charities, non-profit organisations, societies, professional associations, universities, central government and local authorities, international bodies (e.g. WHO, World Bank), think tanks, patient and consumer groups, etc.

Grey literature can include: clinical study reports, government documents, conference abstracts, organisational reports, pre-prints, regulatory documents, theses, etc.

Grey literature is not collected, stored and organised in a consistent way, and searching for grey literature can be a challenge. You will need to take a different approach to finding grey literature than when you search a database. Some of the online resources used to find grey literature have a very basic search interface. 

Where to find grey literature

Resource Scope 
CityLibrary search Finding grey literature using CityLibrary Search.
BASE - Bielefeld Academic Search Engine One of the world's largest search engines for academic web resources. It is maintained by Bielefeld University Library. Finding grey literature using BASE..
CareSearch  Covers topics related to palliative care. Finding grey literature using CareSearch.
TRIP Medical search engine with emphasis on evidence based medicine.
PsycEXTRA Provides access to technical, annual and government reports, conference papers, newsletters, magazines, newspapers and consumer brochures covering psychology.

Pre-print studies are studies that have been completed but have not gone through the peer-review process that most scientific journals require.

Resource Scope 
Association of Medical Research Charities (AMRC) Open Research Covers a range of health research funded by AMRC.
FocUS Archive  Covers ultrasound research.
HRB Open Research Covers a range of health research funded by HRB.
JMIR Preprints Covers research in digital health.
MedRxiv Covers a broad range of health topics.
Nutrixiv Covers research in food science and nutrition.
Preprints with The Lancet For preprints submitted to The Lancet.
PsyArXiv Covers research in psychology.
SSRN preprint networks Used for sharing early stage research (preprints and working papers). You can register on the SSRN platform and subscribe to relevant networks. Registration is free.
Name Scope
Care Opinion Stories from patients.
Health Foundation: patient experiences Articles, blogs, press releases and reports from the Health Foundation.
Health Talk Online A-Z list of topics with videos of patients talking about their experiences.
Healthwatch: National Reports Library Database of reports produced from patient feedback.
King's Fund: Patient Experience Publications, press releases and blogs from the King's Fund.
Patient Experience Library Reports, policy, guidance and research papers.
Patient Experience Network Aimed at health professionals who wish to improve the experience of patients. Includes, blogs, case studies and reports.
Patient Experience Research Centre: Publications Articles, book chapters, conference proceedings and reports.
Patient Voices Patient stories through videos.
Patients Association News, opinions and analysis, stories and reports.

Help to locate trials that have not been published yet.

Resource Scope Database of publicly and privately funded clinical studies conducted around the world. Published by the US National Library of Medicine.
International Standards Randomised Controlled Trial Number Registry Provides details of proposed and ongoing RCTs.
NIHR: Be part of research  Produced by the National Institute for Health and Care Research. Used to find health and social care research in the UK.
ScanMedicine Database of clinical trials and FDA-approved medical devices developed and funded by the National Institute for Health Research (NIHR).
UK Clinical Research Network (UKCRN) Database of clinical research.
WHO: International Clinical Trials Registry Platform (ICTRP) Aims to make research accessible to all those involved in health care decision making. Provided by World Health Organisation (WHO).
Resource Scope
DART-Europe Partnership of national and university libraries to improve access to European research theses.
EThOS Aims to maximise visibility and availability of UK's doctoral theses.
Open Access Theses and Dissertations Aims to provide access to freely available theses and dissertations.
ProQuest Dissertations and Theses Global Online resource available for University of London students and staff.  Registration to Senate House Library required for remote access.