Funding for this research was provided by:
the National Natural Science Foundation of China (71690235)
the Humanities and Social Science Foundation of Ministry of Education in China (16YJA630017)
Article History
Received: 17 July 2018
Accepted: 8 January 2019
First Online: 22 January 2019
Compliance with ethical standards
:
: The authors declare that there are no conflicts of interest regarding the publication of this paper.