Document is current

Article History

Received: 9 January 2018

Accepted: 11 July 2018

First Online: 24 July 2018

Ethics approval and consent to participate

: Ethics approval for the study was granted by the Ethics Review Committee of Peking University, and all the participants provided signed informed consent at the time of participation. The study methodology was carried out in accordance with approved guidelines.

: Not applicable.

: The authors declare that there are no conflicts of interest.

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