Liu, Yan
Liu, Zhaorui
Liang, Richard
Luo, Yanan
Article History
Received: 8 February 2022
Accepted: 14 March 2022
First Online: 22 March 2022
Declarations
:
: All respondents gave informed written consent before they were interviewed, and ethical approval for collecting data on human subjects was obtained and renewed annually at the Peking University Institutional Review Board (IRB00001052–11015). All methods in this study were performed in accordance with the guidelines of the Declaration of Helsinki.
: Not applicable.
: The authors declare that they have no competing interests.