Text and Data Mining valid from 2018-03-20
Received: 20 November 2016
Accepted: 7 March 2018
First Online: 20 March 2018
Compliance with Ethical Standards
: All procedures performed in this study involving human participants were in accordance with the ethical standards of the institutional 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.
: All authors declare that they do not have any conflict of interest.