1. U.S. Department of Health and Human Services, Health Resources and Services Administration, Maternal and Child Health Bureau, Office of Epidemiology and Research, Rockville, Maryland.
2. Department of Community-Public Health, Johns Hopkins University School of Nursing, Baltimore, Maryland.
3. U.S. Department of Health and Human Services, National Institutes of Health, National Institute on Drug Abuse, Division of Epidemiology, Services and Prevention Research, Prevention Research Branch, Bethesda, Maryland.