1. Clinical Practice Research Datalink2017-09-17https://www.cprd.com/home/
2. Qresearch2017-09-17http://www.qresearch.org/SitePages/Home.aspx
3. ResearchONE2017-09-17Transforming data into knowledge http://www.researchone.org/
4. NIVEL2017-09-18UtrechtNetherlands Institute for Health Services Research NIVELNIVEL Primary Care Database https://www.nivel.nl/en/dossier/nivel-primary-care-database