Funding for this research was provided by:
National Social Science Foundation of China ((Grant No. 15CSH053)
Text and Data Mining valid from 2019-02-04
First Online: 4 February 2019
Compliance with Ethical Standards
: The authors declare that they have no conflict of interest.
: All procedures performed in studies involving human participants were in accordance with the ethical standards of Beijing Normal University and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.
: Informed consent was obtained from all individual participants included in the study.