Funding for this research was provided by:
Japan Society for the Promotion of Science (KAKENHI Grant Number 19K08582, KAKENHI Grant Number 18K10671, KAKENHI Grant Number 17K00855, KAKENHI Grant Number 16K09435)
Text and Data Mining valid from 2019-06-11
Received: 26 April 2019
Accepted: 27 May 2019
First Online: 11 June 2019
Compliance with ethical standards
: The authors have no relationships relevant to the contents of this paper to disclose.
: All the procedures followed were in accordance with the Helsinki Declaration of 1964 and later versions.