Text and Data Mining valid from 2018-02-20
Received: 15 December 2017
Accepted: 14 February 2018
First Online: 20 February 2018
Compliance with ethical standards
: The authors declare that they have no conflict of interest.
: All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.