Funding for this research was provided by:
National Natural Science Foundation of China (81870312)
Text and Data Mining valid from 2019-08-09
Received: 9 May 2019
Accepted: 1 August 2019
First Online: 9 August 2019
Ethics approval and consent to participate
: The research ethics were not required anymore, which had been authorized in the former study according to public policy statements of the dataset.
: Not applicable.
: The authors declare that they have no conflict of interest.