Funding for this research was provided by:
Institute for Information and Communications Technology Promotion (2017-0-00398)
Ministry of Science, ICT and Future Planning (2017R1A2B2008729)
Text and Data Mining valid from 2019-07-09
Received: 2 October 2018
Accepted: 2 July 2019
First Online: 9 July 2019
: The authors declare that they have no competing interests.