1. Center for Injury Research and Prevention, The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania.
2. College of Nursing and Health Professions, Drexel University, Philadelphia, Pennsylvania.
3. Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania.
4. Section of Allergy, The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania.
5. Kentucky Children's Hospital, Lexington, Kentucky.
6. College of Medicine, University of Kentucky, Lexington, Kentucky.