Duan, Jun
Kong, Xiangyong
Li, Qiuping
Hua, Shaodong
Zhang, Sheng
Zhang, Xiaoying
Feng, Zhichun
Article History
Received: 18 December 2015
Accepted: 22 February 2016
First Online: 3 March 2016
Competing interests
: The authors declare no competing financial interests.