Funding for this research was provided by:
Received: 27 December 2018
Accepted: 18 July 2019
First Online: 2 August 2019
Ethics approval and consent to participate
: The Ethics Committee of Justus-Liebig Universtität Gießen approved the protocol of this study (reference number: 206/14). Participants provided their written informed consent for participation.
: Not applicable.
: The authors declare that they have no competing interests.