Funding for this research was provided by:
National Research Foundation of Korea (NRF-2018R1A2B6005559)
Text and Data Mining valid from 2020-03-26
Received: 18 September 2019
Accepted: 9 March 2020
First Online: 26 March 2020
Ethics approval and consent to participate
: This study was approved by the institutional review board (IRB No B-1803/450-305), and informed consent was waived.
: Not applicable
: The authors declare that they have no competing interests.