Text and Data Mining valid from 2017-12-20
Received: 26 October 2016
Accepted: 19 October 2017
First Online: 20 December 2017
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. For this type of study formal consent is not required.