Received: 20 September 2018
Accepted: 30 January 2020
First Online: 10 February 2020
Ethics approval and consent to participate
: The local ethics committee (Ethical Committee at the Faculty of Medicine of the University of Leipzig) confirmed in writing that no formal ethical approval was necessary for this study.
: Not applicable, as the manuscript does not contain any individual person’s data.
: The authors declare that they have no competing interests.