Wang, Yi-Feng
Liu, Feng
Long, Zhi-Liang
Duan, Xu-Jun
Cui, Qian
Yan, Jin H.
Chen, Hua-Fu
Article History
Received: 17 September 2014
Accepted: 18 November 2014
First Online: 9 December 2014
Competing interests
: The authors declare no competing financial interests.