1. Department of Orthopedics and Traumatology , University Hospital Tsaritsa Yoanna – ISUL, Medical University – Sofia , Bulgaria
2. Department of Anatomy , Histology and Embryology, Faculty of Medicine, Medical University – Sofia , Bulgaria
3. Department of General and Clinical Pathology , Faculty of Medicine, Trakia University – Stara Zagora , Bulgaria
4. Department of Orthopedics and Traumatology , UMHAT “Dr Georgi Stranski”, Medical University – Pleven , Bulgaria