Wang, Wanpeng
Zhao, Han
Chen, Baihua
Funding for this research was provided by:
the Education Expenditure of Hunan Province Provincial Finance Department
the National Natural Science Foundation of China
Article History
Received: 19 June 2019
Accepted: 29 January 2020
First Online: 12 February 2020
Competing interests
: The authors declare no competing interests.