- Correspondence to Dr Xiang Qian Lao, Jockey Club School of Public Health and Primary Care, The Chinese University of Hong Kong, School of Public Health, Prince of Wales Hospital, Sha Tin, N.T, Hong Kong SAR, China;
- Received 14 May 2017
- Revised 13 September 2017
- Accepted 11 October 2017
- Published online 15 January 2018.
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