Funding for this research was provided by:
China University of Political Science and Law (Innovative Research Team)
Text and Data Mining valid from 2019-12-01
Received: 20 June 2019
Accepted: 16 December 2019
First Online: 30 December 2019
Ethics approval and consent to participate
: The dataset used in this study is a publicly available dataset. Not applicable.
: Not applicable.
: The authors declare that they have no competing interests.