Funding for this research was provided by:
High Level Research Team Building Plan of Social Sciences in Sichuan Province (43-2)
Advanced Interdisciplinary Innovation Research Project of Sichuan University (skqy201216)
Received: 15 October 2018
Accepted: 4 February 2019
First Online: 14 February 2019
: The authors declare that they have no competing interests.
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