Grey Literature

Clinical Guidelines

• National Clinical Guidelines - Irish clinical guidelines validated by the Department of Health.
• National Guideline Clearinghouse - international clinical practice guidelines 
• NICE - guidance from the UK National Institute for Clinical Excellence 
• SIGN - Scottish Intercollegiate Guidelines Network 
• The Guidelines International Network (G-I-N) - development of guidelines and their application into practice. 

Alternatively, if you know the name of a guideline or organisation that publishes guidelines on a particular specialty, you can search for the guideline or organisation in Google. 

Clinical Trial Registers

• ClinicalTrials.gov - the largest registry of clinical trials, run by the United States National Library of Medicine (NLM) at the National Institutes of Health.  
• EU Clinical Trial Register - interventional clinical trials that are conducted in the European Union (EU) and the European Economic Area (EEA).
• ISRCTN Registry - Global registry of trials. 
• WHO International Clinical Trials Registry Platform - aims to facilitate the prospective registration of the WHO Trial Registration Data Set on all clinical trials, and the public accessibility of that information.

Conference Proceedings

Many conference proceedings are available through particular academic databases such as 

• Embase
• SCOPUS
• Web of Science

Select Conference or Conference Proceedings as content type or use the relevant filter, if available.

Dissertations and Theses

• BASE (Bielefeld) - Academic Search Engine. Under the 'Document Type' field, there is the ability to confine your search to 'Thesis'.
• DART-Europe - E-Thesis Portal. A partnership of national and university libraries and consortia to improve global access to European research theses.
• EThOS - Over 500,000 theses from UK institutions.
• NDLDT - The Networked Digital Library of Theses and Dissertations (NDLTD) is an international organization dedicated to promoting the adoption, creation, use, dissemination, and preservation of electronic theses and dissertations (ETDs).

Health and Statistics

• Centers for Disease Control and Prevention (US) - U.S. Department of Health & Human Services
• Europa European Union information portal Statistics documents  Public Health documents
• Eurostat - EU statistics portal
• Global Health Toolkit from the Health Sciences Library, University of Washington
• NICE (NHS) - Public Health 
• OECD - Organisation for Economic Co-operation and Development  OECD Health statistics publications
• OECD iLibrary - statistics and data library
• Public Health area at the Martindale Center 
• United Nations - international organization
• UNICEF - saves children’s lives, to defend their rights, and to help them fulfil their potential, from early childhood through adolescence
• World Health Organization - is the United Nations agency that connects nations, partners and people to promote health, keep the world safe and serve the vulnerable
• WHO Library Database - indexes WHO's journals, technical reports, governmental and non-governmental health agency material
• WHO Link country statistics - statistics by Country
• WHO Global Health Library - search across global and regional indexes
• WHO Global Health Observatory - epidemiology and statistics 
• WHO World Health Report - statistics

Medical Associations and Organisations Worldwide

• ArabMedicare.com - links to Middle Eastern associations 
• Federation of Islamic Medical Associations - registered body of 23 IMAs and 30 associate members worldwide, representing about 50,000 Muslim medical and health professionals
• International Committee for the Red Cross - operates worldwide, helping people affected by conflict and armed violence and promoting the laws that protect victims of war
• The International Federation of Red Cross and Red Crescent Societies - world's largest humanitarian network
• Malaysian Medical Association - association with the largest number of doctors in Malaysia
• Médecins Sans Frontières - provides medical assistance to people affected by conflict, epidemics, disasters, or exclusion from healthcare
• World Federation for Medical Education -  a non-governmental organisation concerned with education and training of medical doctors worldwide
• World Medical Association - directory of member associations 

Preprints

Research papers that appear prior to the completion of full peer review. They are not as extensively validated as peer reviewed publications and so their data or findings should not be used to inform clinical practice. However, the research they contain will be of interest to those seeking the latest or emerging research in their field. Preprints have proven to be very significant in the early dissemination of Covid-19 related work. Preprints are published on:

Preprint Servers, such as those which appear below. 

• MedRxiv - Preprint server for Health Sciences
• BioRxiv - Preprint server for Biology
• ArXiv - Preprint server for the Sciences, including physics, computer science, quantitative biology, statistics and economics.
• SSRN - preprints papers dedicated to Social Sciences. Since being acquired by Elsevier, it is claimed that the SSRN preprints are included in the SCOPUS database.

PMC (PubMed Central) has since June 2020 been making certain Preprints openly available on their database. 

• Preprints can be searched on PMC using their Preprint filter. 

Europe PMC - Searches across all these preprint sources, as well as other Open Access content, can be made on Europe PMC.

Subject Specific

• POPLINE - publications and resources relating to family planning and reproductive health 
• AIDSinfo - information, guidelines, clinical trials on HIV/AIDS treatment, prevention and research from the US National Institutes of Health.
• Social Care Online - for social work and social care. Research briefings, legislation, reports, government documents and more from the UK's Social Care Institute for Excellence