1. Division of Pediatric Epidemiology and Clinical Research; Department of Pediatrics, University of Minnesota; Minneapolis Minnesota
2. University of Minnesota Masonic Cancer Center; Minneapolis Minnesota
3. Department of Mathematics and Statistics; University of New Mexico; Albuquerque New Mexico
4. Sidney Kimmel Comprehensive Cancer Center; Johns Hopkins University; Baltimore Maryland
5. Children's Hospital of Philadelphia; Philadelphia Pennsylvania
6. Division of Epidemiology, Biostatistics, and Preventive Medicine; Department of Internal Medicine, University of New Mexico; Albuquerque New Mexico