1. Division of Pediatric Palliative Care, Department of Pediatrics, Children's Hospital and Medical Center, Omaha, Nebraska, USA.
2. Department of Biostatistics, University of Nebraska Medical Center, Omaha, Nebraska, USA.
3. Department of Nursing Science, Professional Practice and Quality, Children's National Health System, Washington, DC, USA.
4. Department of Pediatrics, The George Washington University, Washington, DC, USA.