1. Department of Pediatrics; Children's Hospital of Philadelphia; Philadelphia Pennsylvania USA
2. Division of Neonatal-Perinatal Medicine, Department of Pediatrics; Larner College of Medicine at the University of Vermont; Burlington Vermont USA
3. Division of Pediatric Cardiology, Department of Pediatrics; Larner College of Medicine at the University of Vermont; Burlington Vermont USA
4. Departments of Pediatrics, Community Health & Epidemiology; Dalhousie University & IWK Health Centre; Halifax Canada