Text and Data Mining valid from 2018-01-06
Received: 31 July 2017
Accepted: 19 December 2017
First Online: 6 January 2018
Compliance with ethical standards
: Sarah K. Kuhn-Régnier, Michael Stickel, Björn-Christian Link, Henning Fischer, Reto Babst and Frank J. P. Beeres declare that they have no conflict of interest.