Li, X
Liang, Q
Liu, W
Zhang, N
Xu, L
Zhang, X
Zhang, J
Sung, J J Y
Yu, J
Article History
Received: 1 December 2014
Revised: 16 June 2015
Accepted: 28 June 2015
First Online: 17 August 2015
Competing interests
: The authors declare no conflict of interest.