- Correspondence to Dr Li Liu, Department of Epidemiology and Biostatistics, and the Ministry of Education Key Lab of Environment and Health, School of Public Health, Tongji Medical College, Huazhong University of Science and Technology, No.13 of Hangkong Road, Wuhan, Hubei 430030, China
- Accepted September 1, 2015
- First published September 18, 2015.
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