Text and Data Mining valid from 2019-01-22
Received: 21 September 2018
Accepted: 2 November 2018
First Online: 22 January 2019
Compliance with Ethical Standards
: The author declares 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.