- Correspondence to Dr Hualiang Lin, Department of Epidemiology, School of Public Health, Sun Yat-Sen University, Guangzhou, Guangdong, China; ; Dr Xinri Zhang, Department of Respiration, First Hospital of Shanxi Medical University, Taiyuan, Shanxi, China;
- Received July 21, 2020
- Revised April 9, 2021
- Accepted May 4, 2021
- First published June 4, 2021.
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