1. Medica Cor Hospital, ul. “Riga” 35, Zdravets Iztok, 7013 Ruse, Bulgaria
2. Medical Faculty, Medical University of Sofia, ul. Georgi Sofiyski 1, 1431 Sofia, Bulgaria
3. Medical Faculty, Sofia University St. Kliment Ohridski, 1 Kozyak Str., 1407 Sofia, Bulgaria
4. Faculty of Public Health and Health Care, Ruse University Angel Kanchev, ul. “Studentska” 8, 7017 Ruse, Bulgaria