1. Department of Hygiene, Epidemiology and Medical Statistics; School of Medicine; University of Athens; Athens Greece
2. Department of Women's and Children's Health; Uppsala University; Uppsala Sweden
3. Department of Pediatric Hematology-Oncology; ‘Pan. & Agl. Kyriakou’ Children's Hospital; Athens Greece
4. 2nd Department of Pediatrics; Aristotelion University of Thessaloniki; AHEPA General Hospital; Thessaloniki Greece
5. Department of Pediatric Hematology and Oncology; Hippokration Hospital; Thessaloniki Greece
6. Department of Pediatric Haematology-Oncology; ‘Aghia Sophia’ Children's Hospital; Athens Greece
7. Department of Pediatric Hematology-Oncology; University Hospital of Heraklion; Heraklion Greece
8. Haematology-Oncology Unit; First Department of Pediatrics; Athens University Medical School; ‘Aghia Sophia’ Children's Hospital; Athens Greece