1. Vagelos College of Physicians and Surgeons, Columbia University, New York, NY 10032, USA
2. Hunter College, New York, NY 10065, USA
3. Teachers College, Columbia University, New York, NY 10027, USA
4. HIAS, Silver Spring, MD 62471, USA
5. Department of Public Health, University of Copenhagen, 1172 Copenhagen, Denmark
6. Mailman School of Public Health, Columbia University, New York, NY 10032, USA