1. Institute of Biochemistry, Faculty of Medicine, University of Nis, Bulevar, Dr Zorana Djindjica 81, 18000 Nis, Serbia
2. Faculty of Medicine, University of Nis, 18000 Nis, Serbia
3. Medical Faculty, University Maribor, 2000 Maribor, Slovenia
4. Department of Hygiene, Faculty of Medicine, University of Nis, 18000 Nis, Serbia