Hao Wang*, Jing Wang, Miao-Miao Liu, Da Wang, Yu-Qin Liu, Yang Zhao, Mei-Meng Huang, Yang Liu, Jing Sun and Guang-Hui Dong
* Corresponding author: Hao Wang wh54315@163.com
BMC Public Health 2012, 12:967 doi:10.1186/1471-2458-12-967