1. Clinic for Gastroenterology and Hepatology, University Clinical Center of Serbia, 11000 Belgrade, Serbia
2. Clinic for Gastroenterology and Hepatology, University Clinical Center of Nis, 18000 Nis, Serbia
3. Faculty of Medicine, University of Belgrade, 11000 Belgrade, Serbia
4. Clinic for Otorhinolaryngology and Maxillofacial Surgery, University Clinical Center of Serbia, 11000 Belgrade, Serbia
5. Department of Cardiology, University Clinical Hospital Center “Dr. Dragisa Misovic-Dedinje”, 11000 Belgrade, Serbia