1. Department of Pediatrics; Aarhus University Hospital; Aarhus Denmark
2. Danish Cancer Society Research Center; Copenhagen; Denmark
3. Children's Hospital Iceland; Landspitali University Hospital; Reykjavik Iceland
4. Department of Clinical Sciences; Lund, Cancer Epidemiology, Lund University; Sweden
5. Finnish Cancer Registry; Helsinki; Finland
6. Department of Pediatrics; Jorvi Central Hospital; Espoo Finland
7. Faculty of Medicine; University of Iceland; Reykjavik Iceland
8. Icelandic Cancer Registry; Reykjavik; Iceland
9. Norwegian Cancer Registry; Oslo; Norway
10. Department of Clinical Sciences; Pediatric Oncology and Hematology, Skåne University Hospital, Lund University; Lund Sweden