Holz, F.
Birngruber, C. G.
Ramsthaler, F.
Verhoff, M. A.
Article History
Received: 9 May 2018
Accepted: 22 January 2019
First Online: 31 January 2019
Compliance with ethical standards
: Informed consent and permission for publication of photos were given by the volunteers.
: The authors declare that they have no conflict of interest.