1. The University of Hong Kong, Queen Mary Hospital; Department of Pediatrics and Adolescent Medicine; Pokfulam Road Hong Kong China
2. Emma Children's Hospital/Academic Medical Center; Department of Paediatric Oncology; PO Box 22660 Amsterdam Netherlands 1100 DD
3. University Medical Center Groningen and University of Groningen, Beatrix Children's Hospital; Department of Paediatric Oncology; Postbus 30.000 Groningen Netherlands 9700 RB