Fang, Jiao
Gong, Chun
Su, Puyu
Wan, Yuhui
Zhang, Zhihua
Tao, Fangbiao
Sun, Ying
Article History
Received: 18 September 2019
Revised: 18 April 2020
Accepted: 14 May 2020
First Online: 8 June 2020
Competing interests
: The authors declare no competing interests.
: We obtained written informed consent from parents and school teachers, as well as child assent.