1. Department of Pediatrics, Boston University School of Medicine and Boston Medical Center, Boston, Massachusetts
2. Department of Pediatrics, University of Maryland School of Medicine, Baltimore, Maryland
3. Department of Pediatrics, University of Arkansas for Medical Sciences, Little Rock, Arkansas
4. Department of Pediatrics, Hennepin County Medical Center, Minneapolis, Minnesota
5. Department of Community Health Prevention, Drexel University School of Public Health, Philadelphia, Pennsylvania
6. Department of Biostatistics
7. Data Coordinating Center, Boston University School of Public Health, Boston, Massachusetts