1. Princess Máxima Center for Pediatric Oncology; Utrecht Netherlands
2. Department of Oncology and Children's Research Center; University Children's Hospital Zurich; Zurich Switzerland
3. Department of Paediatric Oncology; Emma Children's Hospital, Amsterdam UMC, University of Amsterdam; Amsterdam Netherlands
4. Pediatrics III, Sarcoma Centre, West German Cancer Centre; University Hospital Essen; Essen Germany