Wan, Ping
Liu, Xiaopeng
Xiong, Yan
Ren, Yuping
Chen, Jiang
Lu, Nonghua
Guo, Yuan
Bai, Aiping
Article History
Received: 2 October 2015
Accepted: 2 December 2015
First Online: 7 January 2016
Competing interests
: The authors declare no competing financial interests.