Funding for this research was provided by:
Ministry of Education, Culture, Sports, Science and Technology (No. 16H06435, No. 16H06429, No. 16H21723)
Text and Data Mining valid from 2019-01-14
Received: 20 July 2018
Accepted: 7 January 2019
First Online: 14 January 2019
Compliance with ethical standards
: The author declares that he has no conflict of interest.
: This article does not describe any studies involving human participants or animals.