Liu, Dan
Xu, Heping
Shih, Changming
Wan, Zurong
Ma, Xiaopeng
Ma, Weiwei
Luo, Dan
Qi, Hai
Article History
Received: 29 October 2013
Accepted: 27 August 2014
First Online: 15 October 2014
Competing interests
: The authors declare no competing financial interests.