1. Medical Faculty, Sofia University St. Kliment Ohridski, 1 Kozyak Str., 1407 Sofia, Bulgaria
2. Department of Anesthesiology and Intensive Care, University Hospital Lozenetz, 1 Kozyak Str., 1407 Sofia, Bulgaria
3. First Department of Internal Medicine, Medical Faculty, Medical University of Varna, 9000 Varna, Bulgaria
4. Clinic of Neurology, UMHAT “Sv. Georgi”, Faculty of Medicine, Medical University of Plovdiv, 4000 Plovdiv, Bulgaria
5. Department of Gastroenterology, University Hospital Lozenetz, 1 Kozyak Str., 1407 Sofia, Bulgaria
6. Department of Genetics, Faculty of Biology, Sofia University St. Kliment Ohridski, 8 Dragan Tzankov Str., 1164 Sofia, Bulgaria