1. Clinical Center, Department of Ear, Throat and Nose, Banja Luka, Republic of Srpska, Bosnia and Herzegovina
2. Clinical Center, Department for Pathology, Banja Luka, Republic of Srpska, Bosnia and Herzegovina
3. Clinical Center, Department of Maxillofacial Surgery, Banja Luka, Republic of Srpska, Bosnia and Herzegovina
4. University of Belgrade, Clinic Faculty of Medicine, Clinical Center of Serbia, of Allergy and Clinical Immunology, Belgrade, Serbia