1. NHS Right Care (2013) NHS atlas of variation in healthcare. http://www.rightcare.nhs.uk/index.php/nhs-atlas/
2. Instituto Aragonés de Ciencias de la Salud (2013) Atlas de Variaciones en la Práctica Médica en el Sistema Nacional De Salud. http://www.atlasvpm.org/avpm/
3. Bertelsmann Stiftung (2013) Faktencheck Gesundheit. https://faktencheck-gesundheit.de
4. The Dartmouth Institute for Health Policy and Clinical Practice (2013) Dartmouth atlas of health care. http://www.dartmouthatlas.org/
5. Instituto Aragonés de Ciencias de la Salud (2013) The European Collaboration for Health Optimization project (ECHO). http://www.echo-health.eu/?site