1. Department of Otorhinolaryngology; “Dr Vukan Cupic” Mother and Child Health Institute of Serbia; Belgrade Serbia
2. Department of Pulmonology; “Dr Vukan Cupic” Mother and Child Health Institute of Serbia; Belgrade Serbia
3. School of Medicine; University of Belgrade; Belgrade Serbia
4. Institute for Medical Statistics; Belgrade Serbia
5. Clinic for Pediatrics; “Dr Vukan Cupic” Mother and Child Health Institute of Serbia; Belgrade Serbia