Funding for this research was provided by:
China Development Research Foundation (N/A)
Text and Data Mining valid from 2019-06-27
Received: 4 November 2018
Accepted: 18 June 2019
First Online: 27 June 2019
Ethics approval and consent to participate
: Ethical approval was obtained from the Peking University Institutional Review Board (number 2017076). All participants provided informed consent.
: Not applicable.
: The authors declare no competing interests.