1. Childhood Cancer Research Unit, Department of Woman and Child Health
2. Division of Clinical Cancer Epidemiology, Department of Oncology and Pathology, Karolinska Institutet, Karolinska Hospital, Stockholm, Sweden
3. Dana Farber Cancer Institute, The Phyllis F. Cantor Center, Boston, Massachusetts
4. Division of Clinical Cancer Epidemiology, Department of the Sahlgrenska Academy, Gothenburg, Sweden