Funding for this research was provided by:
Japan Society for the Promotion of Science (JP15K18228)
University of the Ryukyus (Okinawa Research Core for Highly Innovative Discipline Science)
Text and Data Mining valid from 2018-04-12
Received: 28 November 2017
Accepted: 3 April 2018
First Online: 12 April 2018
: The authors declare that they have no competing interests.
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