1. Research Institute, Medical University Pleven, 5800 Pleven, Bulgaria
2. Department of Gynecology, Hospital “Saint Anna”, Medical University “Prof. Dr. Paraskev Stoyanov”, 9002 Varna, Bulgaria
3. Department of Obstetrics and Gynecology, Helios Hospital Müllheim, 79379 Müllheim, Germany
4. Faculty Associate, Medical Center, University of Freiburg, 79106 Freiburg, Germany
5. Department of Gynecologic Oncology, Medical University Pleven, 5800 Pleven, Bulgaria
6. Department of Gynecologic Oncology, Ankara Bilkent City Hospital, Maternity Hospital, 06800 Ankara, Turkey
7. Department of General and Clinical Pathology, University Hospital “Dr. Georgi Stranski”, 5800 Pleven, Bulgaria