- Correspondence to Dr Shaonong Dang, Department of Epidemiology and Biostatistics, Xi'an Jiaotong University Health Science Center, Xi'an, Shaanxi 710061, China;
- Received September 3, 2020
- Revision received December 19, 2020
- Accepted December 23, 2020
- First published January 13, 2021.
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