Text and Data Mining valid from 2018-12-13
Received: 29 October 2018
Accepted: 4 December 2018
First Online: 13 December 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. For this type of study formal consent is not required.