Text and Data Mining valid from 2019-01-11
Received: 30 July 2018
Revised: 17 December 2018
Accepted: 31 December 2018
First Online: 11 January 2019
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.