1. Department of Pediatric Hematology and Oncology, University Medicine of Greifswald, Ferdinand-Sauerbruch-Strasse, 17475 Greifswald, Germany
2. Department of Pediatric Oncology and Hematology, Jagiellonian University Medical College, 265 Wielicka Str., 30-663 Krakow, Poland
3. Department of Pediatrics, Hemato-Oncology and Gastroenterology, Pomeranian Medical University, Ul. Unii Lubelskiej 1, 71-252 Szczecin, Poland