1. Department of Physical Medicine & Rehabilitation, University of Colorado School of Medicine and The Children's Hospital, Denver, CO, USA,
2. Colorado Department of Public Health and Environment, Denver, CO, USA
3. Department of Neurology, University of Rochester College of Medicine and Dentistry, Rochester, NY, USA
4. New York Department of Health, Troy, NY, USA
5. Department of Pediatrics, University of Iowa College of Medicine, Iowa City, IA, USA
6. The Departments of Pediatrics and Neurology and the Steele Research Center, University of Arizona College of Medicine, Tucson, AZ, USA
7. Department of Epidemiology, The University of Iowa College of Public Health, Iowa City, IA, USA