Funding for this research was provided by:
Ministry of Education, Culture, Sports, Science and Technology (26340029)
Text and Data Mining valid from 2019-04-09
Received: 3 October 2018
Accepted: 3 April 2019
First Online: 9 April 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.