1. Department of Hepatic; Gastrointestinal and Paediatric surgery; Oslo University Hospital - Rikshospitalet; Oslo Norway
2. Service of Statistics; Institut Curie; Paris France
3. Pediatric Surgery Unit-Women's and Children Health Department; University Hospital of Padua; Italy
4. Department of Paediatric Haematology-Oncology; Giannina Gaslini Children's Hospital; Genova Italy
5. Department of Paediatric Oncology; Institut Curie; Paris France
6. Department of Paediatric Surgery; St Georges Hospital; London United Kingdom