Funding for this research was provided by:
Deutsche Forschungsgemeinschaft (#HA5399/3-1, #HA5399/3-1)
Received: 26 September 2017
Accepted: 8 May 2018
First Online: 14 June 2018
Ethics approval and consent to participate
: The study was approved by the University of Freiburg Ethics Committee and written informed consent was obtained from all participants.
: The authors declare that they have no competing interests.
: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.