- Correspondence to Liming Li, one of the Hangzhou Qian River Scholars, Department of Epidemiology and Biostatistics, School of Public Health, Peking University Health Science Center, 38 Xueyuan Road, Beijing 100191, China;
- Received April 29, 2011
- Accepted November 16, 2011
- First published December 16, 2011.
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