1. National Guideline Clearinghouse™ (NGC), sponsored by the Agency for Healthcare Research and Quality (AHRQ), U.S. Department of Health and Human Services, USA. URL: http://www.guideline.gov/
2. Agency for Quality in Medicine aqumed (Aerztliches Zentrum für Qualität in der Medizin aezq), Berlin, Germany, owned by the German Medical Association (BAEK) and the National Association of Statutory Health Insurance Physicians (KBV), Germany. URL: http://www.aezq.de
3. Programma Nazionale Linee Guida, from Piano nazionale per le linee guida (PNLG), Italy URL: http://www.pnlg.it
4. National Institute for Health and Clinical Excellence (NICE), England, UK. URL: http://www.nice.org.uk
5. Guidelines International Network — G.I.N., Scotland, UK. URL: http://www.g-i-n.net