Text and Data Mining valid from 2019-01-14
Received: 21 May 2018
Accepted: 11 October 2018
First Online: 14 January 2019
Compliance with ethical standards
: Drs. Kyoji Ito, Yusuke Suka, Motoki Nagai, Keishi Kawasaki, Mariko Yamamoto, Daisuke Koike, Yukihiro Nomura, Nobutaka Tanaka, Yoshikuni Kawaguchi have no conflicts of interest or financial ties to disclose.