1. The University of Hong Kong, Faculty of Education, Hong Kong
2. Department of Applied Social Sciences, The Hong Kong Polytechnic University, Hong Kong
3. Public Policy Research Institute, The Hong Kong Polytechnic University, Hong Kong
4. Kiang Wu Nursing College of Macau, Macau
5. Division of Adolescent Medicine, Department of Pediatrics, University of Kentucky College of Medicine, Lexington, KY 40506, USA