Funding for this research was provided by:
the 2016 Social science and economics? association research topics in Henan province (SKL-2016-3868)
National Natural Science Foundation of China (61374028)
the Key Scientific Research Foundation of Education Bureau of Henan Province (19A140021)
Article History
Received: 13 June 2017
Accepted: 31 December 2018
First Online: 10 January 2019
Compliance with ethical standards
:
: All authors declare that they have no conflict of interest.