Huang, K
Guo, S T
Shattuck, M R
Chen, S T
Qi, X G
Zhang, P
Li, B G
Article History
Received: 11 December 2013
Revised: 13 July 2014
Accepted: 12 August 2014
First Online: 5 November 2014
Competing interests
: The authors declare no conflict of interest.