Funding for this research was provided by:
National Research Foundation of Korea (NRF-2018M2A2A6A05057264)
Rural Development Administration, Republic of Korea (PJ012214)
Text and Data Mining valid from 2019-02-01
Received: 25 October 2018
Accepted: 8 January 2019
First Online: 8 February 2019
Compliance with ethical standards
: The authors declare that they have no conflict of interest.
: This study does not include human or animal subjects.