Funding for this research was provided by:
International (Regional) Joint Research Project of the National Natural Science Foundation of China (31671281, 31761143009)
Text and Data Mining valid from 2018-12-10
Received: 31 July 2018
Accepted: 3 December 2018
First Online: 10 December 2018
Compliance with ethical standards
: The authors declare that there are no conflicts of interest.