1. Drexel School of Public Health, Drexel University, 245 N. 15th Street, Mail Stop 660, Philadelphia, PA 19102, USA
2. Drexel College of Nursing and Health Professions, Drexel University, 245 N. 15th Street, Mail Stop 1030, Philadelphia, PA 19102, USA
3. The Research Center, Franciscan Hospital for Children, 30 Warren Street, Brighton, MA 02135, USA
4. Department of Pediatrics, St. Christopher's Hospital for Children, 3601 A Street, Philadelphia, PA 19134, USA