Chen, C
Wang, X
Xiong, X
Liu, Q
Huang, Y
Xu, Q
Hu, J
Ge, G
Ling, K
Article History
Received: 26 September 2013
Revised: 27 December 2013
Accepted: 17 October 2014
First Online: 8 December 2014
Competing interests
: The authors declare no conflict of interest.