Du, T
Shi, G
Li, Y M
Zhang, J F
Tian, H W
Wei, Y Q
Deng, H
Yu, D C
Article History
Received: 11 April 2014
Revised: 14 June 2014
Accepted: 17 June 2014
First Online: 18 July 2014
Competing interests
: The authors declare no conflict of interest.
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