Kröll, A.-K.
Schaefer, N.
Kiefer, A.
Schmidt, P.
Article History
First Online: 9 January 2018
Compliance with ethical guidelines
:
: A.-K. Kröll, N. Schaefer, A. Kiefer and P. Schmidt declare that they have no competing interests.
: The investigations were carried out according to the specifications of the Central Ethics Committee of the Federal Medical Council.