1. Department of Paediatric Haematology and Oncology University Hospital “Tzaritza Giovanna – ISUL” Sofia Bulgaria
2. Centre for Coagulopathies and Rare Anaemias University Hospital “Sv. Marina” Varna Bulgaria
3. Department of Paediatrics University Hospital “G. Stranski” Pleven Bulgaria
4. Department of Haematology Military Hospital Sofia Bulgaria
5. Faculty of Statistics Technical University Dortmund Germany
6. Institute of Transfusion Medicine and Experimental Haematology Bonn Germany