Text and Data Mining valid from 2019-01-14
Received: 19 October 2018
Accepted: 3 January 2019
First Online: 14 January 2019
Compliance with ethical standards
: No funding was received for this study.
: The authors declare that they have no conflict of interest.
: All procedures performed in this study were in accordance with the ethical standards of our institutional review board and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards. For this type of study formal consent is not required.
: For this type of retrospective study formal consent is not required.