Text and Data Mining valid from 2019-10-31
Received: 20 June 2019
Accepted: 9 October 2019
First Online: 31 October 2019
Ethics approval and consent to participate
: This study obtained exemption from Institutional Review Board (IRB) of Jichi Medical University, Saitama Medical Centre, and the need for informed consent was waived due to the nature of the study.
: Not applicable.
: The authors declare that they have no competing interests.