Text and Data Mining valid from 2019-02-13
Received: 22 October 2018
Accepted: 6 February 2019
First Online: 13 February 2019
Compliance with ethical standards
: Drs. Yasuki Hori, Kazuki Hayashi, Itaru Naitoh, Hiroyuki Kato, Tatsuma Nomura, Katsuyuki Miyabe, Michihiro Yoshida, Naruomi Jinno, Makoto Natsume, Akihisa Kato, Go Asano, Shuji Takiguchi, and Kiyokazu Nakajima have no conflicts or interest of financial ties to disclose.