Pietzner, J
Merscher, B M
Baer, P C
Duecker, R P
Eickmeier, O
Fußbroich, D
Bader, P
Del Turco, D
Henschler, R
Zielen, S
Schubert, R
Article History
Received: 9 July 2015
Revised: 29 November 2015
Accepted: 1 December 2015
First Online: 11 January 2016
Change Date: 6 April 2015
Change Type: Update
Change Details: This paper was modified 12 months after initial publication to switch to Creative Commons licence terms, as noted at publication
Competing interests
: The authors declare no conflict of interest.