1. Albert Einstein College of Medicine, Departments of Epidemiology and of Emergency Medicine, Bronx, NY, USA
2. McGill University and Jewish General Hospital, Center for Clinical Epidemiology and Community Studies, Montreal, Qc, Canada
3. McGill University and Montreal Children's Hospital, Montreal, Qc, Canada
4. McGill University and Royal Victoria Hospital, Division of Vascular Surgery, Montreal, Qc, Canada