Funding for this research was provided by:
Ministry of Health and Welfare (HI12C0756)
Text and Data Mining valid from 2018-12-07
Received: 11 September 2018
Accepted: 11 November 2018
First Online: 7 December 2018
Compliance with ethical standards
: The authors declare that they have no conflict of interest.
: For this type of study formal consent is not required.