Funding for this research was provided by:
Grants-in-Aid for Scientific Research from the Ministry of Education, Science, Sports, and Culture of Japan (22591540)
Text and Data Mining valid from 2019-08-13
Received: 30 May 2019
Accepted: 4 August 2019
First Online: 13 August 2019
Compliance with ethical standards
: The authors have declared that no conflict of interest exists.