Funding for this research was provided by:
National Natural Science Foundation of China (61703014, 71704007)
Base Project of Beijing Social Science Foundation (17JDGLB019)
Text and Data Mining valid from 2019-03-22
First Online: 22 March 2019
Compliance with ethical standards
: The authors declare that they have no conflict of interest.
: This article does not contain any studies with human participants or animals performed by any of the authors.