Text and Data Mining valid from 2019-01-14
Received: 9 February 2018
Accepted: 5 January 2019
First Online: 14 January 2019
Compliance with ethical standards
: The authors declare that they have no conflicts 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.
: No informed consent was required due to the retrospective nature of the study.