Text and Data Mining valid from 2019-03-14
Received: 27 August 2018
Accepted: 6 March 2019
First Online: 14 March 2019
Compliance with ethical standards
: Jun Watanabe, Atsushi Ishibe, Yusuke Suwa, Hirokazu Suwa, Mitsuyoshi Ota, Chikara Kunisaki, and Itaru Endo have no conflicts of interest or financial ties to disclose.