1. Department of Orthopedics and Traumatology, Faculty of Medicine, Medical University—Pleven, 5800 Pleven, Bulgaria
2. IPSMP Rheumatology, 6000 Stara Zagora, Bulgaria
3. Department of Health Care, Faculty of Medicine, Trakia University, 6015 Stara Zagora, Bulgaria
4. Faculty of Public Health and Healthcare, University “Prof Dr Asen Zlatarov”—Burgas, 8010 Burgas, Bulgaria