Wang, Shuping
Xu, Jin
Jiang, Xiaofeng
Li, Chaofan
Li, Hongmin
Song, Suhang
Huang, Erdan
Meng, Qingyue
Article History
Received: 28 August 2018
Accepted: 20 November 2018
First Online: 4 December 2018
Ethics approval and consent to participate
: Informal consent was obtained for all study participants and government permission received prior to data collection.
: Individual level data is not published in this manuscript.
: The authors declare that they have no competing interests.
: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.