Sun, X
Mao, Y
Wang, J
Zu, L
Hao, M
Cheng, G
Qu, Q
Cui, D
Keller, E T
Chen, X
Shen, K
Wang, J
Article History
Received: 27 January 2014
Revised: 22 April 2014
Accepted: 24 April 2014
First Online: 9 June 2014
Competing interests
: The authors declare no conflict of interest.