Lu, G
Teng, X
Zheng, Z
Zhang, R
Peng, L
Zheng, F
Liu, J
Huang, H
Xiong, H
Article History
Received: 4 June 2015
Revised: 25 November 2015
Accepted: 31 December 2015
First Online: 11 January 2016
Competing interests
: The authors declare no conflict of interest.