1. Division of Pediatric Hematology-Oncology, University Medical Center, Freiburg, Germany
2. Department of Pediatrics, Aarhus University Hospital Skejby, Aarhus, Denmark
3. Department of Pediatric Hematology-Oncology, University Children's Hospital, Zürich, Switzerland
4. Department of Pediatric Oncology/Hematology, Erasmus Medical Center and DCOG, Rotterdam, The Netherlands
5. Pediatric Hematology-Oncology, University of Pavia Fondazione IRCCS Policlinico San Matteo, Pavia, Italy