1. Division of Pediatric Hematology-Oncology and Stem Cell Transplantation; Children and Adolescents; Helsinki University Hospital; Helsinki Finland
2. Department of Pediatric Oncology; Astrid Lindgren Children's Hospital; Stockholm Sweden
3. Childhood Cancer Research Unit; Department of Women's and Children's Health; Karolinska Institute; Stockholm Sweden
4. Institute of Gynegology, Obstetrics; and Pediatrics; University of Copenhagen; Copenhagen Denmark
5. Department of Pediatrics; University Hospital Rigshospitalet; Copenhagen Denmark
6. Unit of Biostatistics; Institute of Environmental Medicine; Karolinska Institutet; Stockholm Sweden
7. Department of Pediatrics; Drammen Hospital; Oslo Norway
8. Children's Hospital; Landspitali University Hospital; Reykjavik Iceland
9. Children's Hospital; Turku University Hospital; Turku Finland