Text and Data Mining valid from 2019-04-15
Received: 31 October 2018
Accepted: 7 March 2019
First Online: 15 April 2019
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 international and 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.