Zhang, Xuliang
Cui, Haiqin
Humayun, Muhammad
Qu, Yang
Fan, Naiying
Sun, Xiaojun
Jing, Liqiang
Article History
Received: 10 November 2015
Accepted: 22 January 2016
First Online: 24 February 2016
Competing interests
: The authors declare no competing financial interests.