Text and Data Mining valid from 2019-01-09
Received: 2 January 2019
Accepted: 4 January 2019
First Online: 9 January 2019
Compliance with ethical standards
: All 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 institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.
: Informed consent was obtained from all individual participants included in the study.