1. Tobacco Control Unit, Cancer Council Victoria, 100 Drummond Street Carlton, VIC 3053, Australia
2. Cancer Research UK, Health Behaviour Unit, Department of Epidemiology and Public Health, University College, London WC1E6XA, UK
3. Department of Psychology, University of Waterloo, 200 University Avenue West, Waterloo, ON, Canada N2L 3G1
4. Department of Health Behavior, Roswell Park Cancer Institute, Elm and Carlton Streets, Buffalo, NY 14263, USA
5. Department of Public Health, University of Otago Wellington, P.O. Box 7343, Wellington South 6242, New Zealand