1. a Division of HIV/AIDS, U.S. Department of Health and Human Services , National Center for Infectious Diseases, Centers for Disease Control , Atlanta , Georgia
2. b Drug Abuse Prevention and Treatment , New York , New York
3. c Comprehensive Drug Research Cenler, University of Miami , Miami , Florida
4. d Bayview-Hunter's Point Foundation , San Francisco , California
5. e California State University , Hayward , California
6. f Columbia University , New York , New York