Funding for this research was provided by:
Bundesministerium für Bildung und Forschung (01EO1401)
Article History
Received: 11 February 2018
Revised: 15 May 2018
Accepted: 17 May 2018
First Online: 30 May 2018
Compliance with ethical standards
:
: The authors declare that they have no conflict of interest.
: The study accorded to the ethical principles laid down in the 1964 Declaration of Helsinki and its later amendments and was approved by the Technical University of Munich Ethics Committee. All participants gave their informed consent prior to their inclusion in the study.