- Correspondence to Professor Linwei Tian, 4/F, The Jockey Club School of Public Health and Primary Care, The Chinese University of Hong Kong, Prince of Wales Hospital, Sha Tin-NT, Hong Kong;
- Received 20 August 2012
- Revised 4 January 2013
- Accepted 10 February 2013
- Published online 2 May 2013.
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