1. Paediatric Palliative Care Centre, Children's and Adolescents' Hospital Datteln, Department of Children's Pain Therapy and Paediatric Palliative Care Witten/Herdecke University, Datteln, Germany.
2. School of Nursing Science, Witten/Herdecke University, Witten, Germany.
3. Pediatric Palliative Care Service, Children's Hospital Boston, Dana-Farber Cancer Institute, Harvard Medical School Boston, Massachusetts.