Funding for this research was provided by:
Text and Data Mining valid from 2018-09-11
Received: 8 May 2018
Revised: 26 August 2018
Accepted: 30 August 2018
First Online: 11 September 2018
Compliance with ethical standards
: This work was supported by the Soonchunhyang University Research Fund.
: The authors declare that they have no conflict of interest.