Hege, M A
Stingl, K T
Kullmann, S
Schag, K
Giel, K E
Zipfel, S
Preissl, H
Article History
Received: 6 February 2014
Revised: 15 April 2014
Accepted: 15 May 2014
First Online: 9 June 2014
Competing interests
: The authors declare no conflict of interest.