Funding for this research was provided by:
Humanities and Social Science Foundation of Ministry of Education of China (18YJC880005)
Text and Data Mining valid from 2019-05-30
First Online: 30 May 2019
Compliance with ethical standards
: The authors declare that they have no conflict of interest.
: All procedures performed in studies involving human participants are in accordance with the ethical standards of the institutional 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.