Funding for this research was provided by:
The advanced research programme (Kodo Kenkyuu) sponsored by Tokyo Metropolitan Government
Text and Data Mining valid from 2019-09-19
Received: 8 October 2018
Revised: 15 August 2019
Accepted: 14 September 2019
First Online: 19 September 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.