Funding for this research was provided by:
National Natural Science Foundation of China (No. 61502294)
the CERNET Innovation Project (NGII20170513,NGII20170206)
Text and Data Mining valid from 2019-11-08
Received: 3 July 2019
Accepted: 11 September 2019
First Online: 8 November 2019
: The authors declare that they have no competing interests.