[1] Curtin Univ, Fac Hlth Sci, Natl Drug Res Inst, Bentley, WA 6102, Australia
[2] Aarhus Univ, Ctr Alcohol & Drug Res, DK-8000 Aarhus C, Denmark
[3] UNSW Australia, Natl Drug & Alcohol Res Ctr, Drug Policy Modelling Program, Sydney, NSW, Australia
[4] London S Bank Univ, Dept Social Sci, London, England