Text and Data Mining valid from 2019-05-17
Received: 27 November 2018
Revised: 28 March 2019
Accepted: 10 April 2019
First Online: 17 May 2019
Compliance with ethical guidelines
: E. Tackmann and S. Dettmer declare that they have no competing interests.
: For this article no studies with human participants or animals were performed by any of the authors. All studies performed were in accordance with the ethical standards indicated in each case.