The acknowledgement goes to all members of the rating group: Corrado Bait, Etienne Cavaignac, Riccardo Cristiani, Markas Fiodorovas, Gijs Helmerhorst, Christian Hoser, Mustafa Karahan, George Komnos, Koen Carl Lagae, Vincenzo Madonna, Eduardo Monaco, Juan Carlos Monllau, Matthieu Ollivier, Mikko Ovasaka, Wolf Petersen, Tomasz Piontek, James Robinson, Kristian Samuelson, Sven Scheffler, Bertrand Sonnery-Cottet, the ESSKA office (special thanks to Anna Hansen for administrative support) and to Judy C Mac Donald (proof reading) as well as the peer reviewers of the affiliated national societies (BAKAST, BKS, AOTBIH, CSSTA, SAKS, EASTS, FAKA, SFA, GASSA, AGA, GOTS, DKG, HAA, SIAGASCOT, LAKAS, LIROMS, NVA, NAA, PTA, SPAT, SPOT, SRATS, ASTAOR, RKA, ASTAS, SSASST, SEROD, AEA, SETRADE, SFAIM, TUSYAD, BOSTAA) for their review.