1. Special Hospital for Lung Diseases “Ozren”, Sokobanja, Serbia
2. University of Niš, Faculty of Medicine, Department of Internal medicine, Niš, Serbia
3. University of Niš, Faculty of Medicine, Institute of Biochemistry, Niš, Serbia
4. University of Novi Sad, Faculty of Technical Sciences, Serbia
5. University of Kragujevac, Faculty of Medical Sciences, Department of Internal Medicine, Kragujevac, Serbia