- Correspondence to Dr Youjie Wang, School of Public Health, Tongji Medical College, Huazhong University of Science and Technology, Hangkong Road 13, Wuhan, Hubei 430030, China;
- Received January 19, 2015
- Revised April 26, 2015
- Accepted May 3, 2015
- First published May 20, 2015.
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