1. Department of Prosthetic Dentistry, Faculty of Dental Medicine, Medical University-Plovdiv, 4000 Plovdiv, Bulgaria
2. Department of Healthcare Management, Faculty of Public Health, Medical University-Plovdiv, 4000 Plovdiv, Bulgaria
3. Department of Medical Informatics, Biostatistics and eLearning, Faculty of Public Health, Medical University-Plovdiv, 4000 Plovdiv, Bulgaria
4. Department of Prosthetic Dentistry, Faculty of Dental Medicine, Medical University-Sofia, 1431 Sofia, Bulgaria