Fan, Xiaojing
Su, Min
Zhao, Yaxin
Si, Yafei
Zhou, Zhongliang
Article History
Received: 29 January 2021
Accepted: 31 May 2021
First Online: 16 June 2021
Declarations
:
: Ethical approval for collecting data on human subjects was received at Peking University by their institutional review board (IRB). This approval is updated annually. All subjects gave their informed consent for inclusion before they participated in the survey. We confirm that all methods were carried out in accordance with relevant guidelines and regulations.
: Not Applicable.
: The authors declare that they have no competing interests.