Li, Shanshan
Wang, Rui
Li, Deyong
Ma, Jing
Li, Heng
He, Xiaochuan
Chang, Zengyi
Weng, Yuxiang
Article History
Received: 25 November 2013
Accepted: 11 April 2014
First Online: 29 April 2014
Competing interests
: The authors declare no competing financial interests.