1. Daugavpils Regional Hospital, Vasarnicu Street 20, LV-5417 Daugavpils, Latvia
2. Department of Doctoral Studies, Riga Stradins University, Dzirciema Street 16, LV-1007 Riga, Latvia
3. Department of Otorhinolaryngology, Riga Stradins University, Pilsonu Street 13, LV-1002 Riga, Latvia
4. Pauls Stradins Clinical University Hospital, Pilsonu Street 13, LV-1002 Riga, Latvia
5. Institute of Anatomy and Anthropology, Riga Stradins University, Kronvalda Boulevard 9, LV-1010 Riga, Latvia
6. Children University Hospital, Vienibas gatve 45, LV-1004 Riga, Latvia