Text and Data Mining valid from 2018-05-02
Received: 20 June 2017
Accepted: 25 April 2018
First Online: 2 May 2018
Compliance with Ethical Standards
: 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.
: The authors declare that they have no conflict of interest.