Text and Data Mining valid from 2019-02-06
First Online: 6 February 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.
: Informed consent was obtained from all individual participants included in the study.
: All authors declare that there is no conflict of interest.