Funding for this research was provided by:
Deutsche Forschungsgemeinschaft (HO 5456/3-1)
Text and Data Mining valid from 2019-10-17
Received: 7 June 2019
Revised: 6 September 2019
Accepted: 10 September 2019
First Online: 17 October 2019
Compliance with ethical standards
: The study was conducted according to the Declaration of Helsinki and was approved by the ethics committee of Heinrich Heine University Duesseldorf, Germany, (reference number 4969) and written informed consent was obtained.
: The authors declare that there is no conflict of interest.