Funding for this research was provided by:
Ministry of Education, Culture, Sports, Science and Technology (Kiban B: 17H03647)
Text and Data Mining valid from 2019-03-15
Received: 6 January 2019
Accepted: 28 February 2019
First Online: 15 March 2019
Compliance with Ethical Standards
: The authors declare that they have no conflict of interest.
: This article does not contain any studies with human participants or animals performed by any of the authors.