Funding for this research was provided by:
Hong Kong Council on Smoking and Health (260007591)
Received: 17 January 2018
Accepted: 12 December 2018
First Online: 7 January 2019
Ethics approval and consent to participate
: This study have been approved by the Institutional Review Board of the University of Hong Kong and Hospital Authority Hong Kong West Cluster (reference UW14-412). Written consent was obtained from the participants’ parents after fully informing them of the study’s purpose and details.
: Not applicable.
: The authors declare that they have no competing interests.
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