Text and Data Mining valid from 2019-10-16
Received: 8 October 2018
Accepted: 9 October 2019
First Online: 16 October 2019
Compliance with ethical standards
: Drs. Tatsuma Nomura, Ippei Matsuzaki, Shinya Sugimoto, Jun Oyamda, Akira Kamei, and Makoto Kobayashi have no conflicts of interest or financial ties to disclose.