TY - JOUR A1 - Boily, M.C. A1 - Baggaley, R.F. A1 - Wang, L. A1 - Masse, B. A1 - White, R.G. A1 - Hayes, R.J. A1 - Alary, M. T1 - Heterosexual risk of HIV-1 infection per sexual act: systematic review and meta-analysis of observational studies Y1 - 2009 DO - 10.1016/S1473-3099(09)70021-0 JF - Lancet Infectious Diseases VL - 9 IS - 2 ER -