1. Department of Epidemiology, Biostatistics and Occupational Health; McGill University; Montreal QC Canada
2. Department of Epidemiology, Gillings School of Global Public Health; University of North Carolina; Chapel Hill NC U.S.A.
3. Department of Obstetrics and Gynecology and Global Health Institute; Duke University; Durham NC U.S.A.
4. Division of Epidemiology, Statistics and Prevention Research; NICHD, NIH; Bethesda MD U.S.A.