Pan, Jinghu
Hu, Yanxing
Funding for this research was provided by:
National Natural Science Foundation of China (41661025)
Scientific Research Fund for the Provincial Universities of Gansu (2016A-003)
the Research ability promotion project for young teachers of Northwest Normal University (NWNU-LKQN-16-7)
Article History
Received: 26 April 2017
Accepted: 14 March 2018
First Online: 24 May 2018
Compliance with Ethical Standards
:
: The authors declare that they have no conflict of interest.