Text and Data Mining valid from 2019-01-25
First Online: 25 January 2019
Compliance with Ethical Standards
: This research was conducted in compliance with Code of Conduct Social Science Research UNESCO (ExternalRef removed) and “Conduct for Responsible Research Activities” published by Japan Science and Technology Agency (ExternalRef removed).
: Informed consent was obtained from all individual participants included in the study.
: The authors declare that they have no conflict of interests.