Di Gioia, D
Stieber, P
Schmidt, G P
Nagel, D
Heinemann, V
Baur-Melnyk, A
Article History
Received: 24 August 2014
Revised: 8 December 2014
Accepted: 21 December 2014
First Online: 3 February 2015
Competing interests
: The authors have declared no conflicts of interest.