Text and Data Mining valid from 2019-09-09
Received: 12 July 2019
Accepted: 3 September 2019
First Online: 9 September 2019
Compliance with ethical standards
: All authors declare that they have no conflict of interest.
: The ethical standards of the responsible committee on human experimentation (institutional and national) and Declaration of Helsinki of 1964 (revised in 2008) were followed.
: The institutional review board of our institution approved the study, and informed consent was waived.