- 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 August 20, 2012
- Revised January 4, 2013
- Accepted February 10, 2013
- First published February 27, 2013.
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