Funding for this research was provided by:
National Research Foundation of Korea (2016R1A2B4011561)
Ministry of Science, ICT and Future Planning (2016M3C7A1904336)
Text and Data Mining valid from 2020-02-21
Received: 12 February 2019
Accepted: 29 January 2020
First Online: 21 February 2020
: The authors declare no competing interests.