1. University Hospital Foča, 73300 Foča, Bosnia and Herzegovina
2. Faculty of Medicine Foča, University of East Sarajevo, 73300 Foča, Bosnia and Herzegovina
3. Clinic of Otorhinolaryngology and Maxillofacial Surgery, Clinical Center of Serbia, 11000 Belgrade, Serbia
4. Faculty of Medicine Belgrade, University of Belgrade, 11000 Belgrade, Serbia
5. Department of Epidemiology, Faculty of Medicine, University of Pristina Temporarily Seated in Kosovska Mitrovica, 38220 Kosovska Mitrovica, Serbia