- Correspondence to Professor Huachun Zou, School of Public Health (Shenzhen), Sun Yat-Sen University, Shenzhen, Guangdong, China; ; Professor Yong Cai, School of Public Health, Shanghai Jiao Tong University, School of Medicine, Shanghai, China;
- Received January 9, 2019
- Revised April 13, 2019
- Accepted April 18, 2019
- First published May 9, 2019.
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