1. Department of Epidemiology, College of Public Health, University of Nebraska Medical Center, Omaha, Nebraska, USA
2. ARC Operational Development, Washington, District of Colombia, USA
3. Brett-Major Law, Bethesda, Maryland, USA
4. Department of Epidemiology, London School of Hygiene and Tropical Medicine, London, UK
5. Veritas Management Group, Alpharetta, Georgia, USA