- Correspondence to Dr Xiaomin Zhang, Department of Occupational and Environmental Health, School of Public Health, Tongji Medical College, Huazhong University of Science and Technology, 13 Hangkong Road, Wuhan, 430030, China;
- Received September 25, 2013
- Revised February 13, 2014
- Accepted February 21, 2014
- First published March 13, 2014.
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