Pak, Yunchol
Yang, Xuejun
Kim, Yongdok
Jong, Chanhong
Kim, Haksong
Lee, Namhyok
Kim, Songgun
Kim, Yongchol
Article History
Received: 9 April 2018
Accepted: 5 July 2018
First Online: 3 September 2018
Ethics approval and consent to participate
: Not applicable.
: Not applicable.
: The authors declare that they have no competing interests.