1. Department of Pediatrics/Pediatric Hematology and Oncology Unit, Medical University Plovdiv, 15A Vasil Aprilov Boulevard, 4000 Plovdiv, Bulgaria
2. Division of Pediatric Hematology and Oncology, Department of Pediatrics and Adolescent Medicine, Medical University Graz, Auenbruggerplatz 34/2, 8036 Graz, Austria