Funding for this research was provided by:
Science & Technology Program of Sichuan (2019YFS0494)
Key Projects of Social Science Planning in Sichuan Province (SC18A013)
Text and Data Mining valid from 2019-08-15
Received: 28 May 2019
Accepted: 9 August 2019
First Online: 15 August 2019
: The authors declare that they have no competing interests.