1. Department of Ear, Nose and Throat Diseases, Medical Faculty, Medical University of Sofia, University Hospital “Tsaritsa Yoanna—ISUL”, Byalo More Str. 8, 1527 Sofia, Bulgaria
2. Laboratory of Genomic Stability, Institute of Molecular Biology, Bulgarian Academy of Sciences, Georgi Bonchev Bl. 21, 1113 Sofia, Bulgaria
3. Molecular Medicine Center, Department of Medical Chemistry and Biochemistry, Medical Faculty, Medical University of Sofia, Zdrave Str. 2, 1431 Sofia, Bulgaria
4. Department of Medical Microbiology, Medical Faculty, Medical University of Sofia, Zdrave Str. 2, 1431 Sofia, Bulgaria
5. Department of Occupational Medicine, Faculty of Public Health, Medical University of Sofia, University Hospital “Tsaritsa Yoanna—ISUL”, Byalo More Str. 8, 1527 Sofia, Bulgaria