1. The European Arthroplasty Register: http://www.ear.efort.org/downloads/EFORT-EAR-Minimal-Dataset-THA-primary.pdf.
2. The Portuguese Arthroplasty Register: http://www.rpa.spot.pt/?lang=en-GB.
3. La Société Française d’Orthopédie. Arthroplasty Register Annual report 2011: http://www.sofcot.fr/10-registre-national/registre-national.asp.
4. The Swedish Hip Arthroplasty Register: http://www.shpr.se/en/default.aspx.
5. The Swedish Knee Arthroplasty Register: http://www.knee.nko.se/english/online/thePages/contact.php.