Received: 24 January 2019
Accepted: 17 June 2019
First Online: 9 July 2019
Ethics approval and consent to participate
: This article does not contain any studies with human participants or animals performed by any of the authors.
: For this type of study, formal consent is not required.
: Frank Schwarz, Maike Langer, Tina Hagena, Brigitte Hartig, Robert Sader, and Jürgen Becker declare that they have no competing interests related to this analysis.