Hager, B
Kraywinkel, K
Keck, B
Katalinic, A
Meyer, M
Zeissig, S R
Scheufele, R
Wirth, M P
Article History
Received: 18 May 2016
Revised: 17 July 2016
Accepted: 9 August 2016
First Online: 13 September 2016
Competing interests
: The authors declare no conflict of interest.