Engel, L A
Wittig, S
Bock, F
Sauerbier, L
Scheid, C
Holtick, U
Chemnitz, J-M
Hallek, M
Cursiefen, C
Steven, P
Article History
Received: 22 August 2014
Revised: 10 February 2015
Accepted: 2 March 2015
First Online: 20 April 2015
Competing interests
: The authors declare no conflict of interest.