Funding for this research was provided by:
Soonchunhyang University (Not applicable)
National Research Foundation of Korea (NRF-2018R1C1B5045312)
Text and Data Mining valid from 2018-11-10
Received: 22 June 2018
Accepted: 1 November 2018
First Online: 10 November 2018
Compliance with ethical standards
: All procedures were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments.
: The authors declare that they have no conflicts of interest.