Funding for this research was provided by:
Institute for Information and Communications Technology Promotion (2017000709)
National Research Foundation of Korea (NRF-2017M3D1A1039288)
Text and Data Mining valid from 2019-03-28
Received: 3 January 2019
Accepted: 28 February 2019
First Online: 28 March 2019
: The authors declare that they have no competing interests.
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