Wang, G
Zhang, Q
Song, Y
Wang, X
Guo, Q
Zhang, J
Li, J
Han, Y
Miao, Z
Li, F
Article History
Received: 9 September 2014
Revised: 21 January 2015
Accepted: 28 January 2015
First Online: 12 March 2015
Competing interests
: The authors declare no conflict of interest.