Xu, H-G
Zhai, Y-X
Chen, J
Lu, Y
Wang, J-W
Quan, C-S
Zhao, R-X
Xiao, X
He, Q
Werle, K D
Kim, H-G
Lopez, R
Cui, R
Liang, J
Li, Y-L
Xu, Z-X
Article History
Received: 16 January 2014
Revised: 5 August 2014
Accepted: 6 August 2014
First Online: 29 September 2014
Competing interests
: The authors declare no conflict of interest.