1. Department of Family Medicine and Community Health; University of Massachusetts Medical School; Worcester, Massachusetts
2. Department of Biostatistics; Boston University School of Public Health; Boston, Massachusetts
3. Section of General Internal Medicine, Department of Medicine; Boston Medical Center, Clinical Addiction Research and Education (CARE) Unit; Boston, Massachusetts
4. Data Coordinating Center, Boston University School of Public Health; Boston, Massachusetts
5. Boston Health Care for the Homeless Program; Boston, Massachusetts
6. Department of Community Health Sciences; Boston University School of Public Health; Boston, Massachusetts
7. Department of Epidemiology; Boston University School of Public Health; Boston, Massachusetts