Received: 8 June 2018
Accepted: 22 May 2019
First Online: 3 June 2019
Ethics approval and consent to participate
: Based on the guidelines of the local Independent Ethics Committee of Ulm University (Ethikkommission der Universität Ulm) no specific ethical approval was required to perform this study. Therefore, ethical approval was not requested. We affirm that we obtained written informed consent from all the participants prior to the study.
: Study participants provided written informed consent for a possible scientific publication of the results.
: The authors declare that they have no competing interests.