Funding for this research was provided by:
National Project for Educational Sciences Planning in China (CBA130126)
Text and Data Mining valid from 2019-03-05
Received: 31 October 2018
Accepted: 3 February 2019
First Online: 5 March 2019
Compliance with Ethical Standards
: The authors declare that they have no conflict of interest.
: All procedures performed in this study were in accordance with the ethical standards of the ethics committee on human experimentation of Shandong Normal University 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.