Text and Data Mining valid from 2018-04-09
Received: 20 November 2017
Accepted: 24 January 2018
First Online: 9 April 2018
: The present study was not required ethical approval.
: Katsuhiro Tsuruta, Yasunori Ayukawa, Tatsuya Matsuzaki, Masafumi Kihara, and Kiyoshi Koyano declare that they have no competing interests.
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