Text and Data Mining valid from 2018-09-15
Received: 11 August 2018
Accepted: 8 September 2018
First Online: 15 September 2018
Compliance with ethical standards
: The authors declare that they have no conflict of interest.
: As this was a retrospective study, this study did not contain any contact with human participants or animals performed by any of the authors.
: As this was a retrospective study, no informed consent was required for this study by the internal review board.