Otsuka, Sadao http://orcid.org/0000-0001-6282-840X
Murai, Toshiya
Article History
Received: 14 May 2019
Accepted: 5 February 2020
First Online: 20 February 2020
Competing interests
: This work was supported by the Japan Kanji Aptitude Testing Foundation (<i>Nihon Kanji Noryoku Kentei Kyokai</i>).