1. University Medical Centre Ljubljana, Department of Otorhinolaryngology and Cervicofacial Surgery, Zaloška 2, 1000 Ljubljana, Slovenia
2. Novo mesto General Hospital, Department of Otorhinolaryngology, Šmihelska cesta 1, 8000 Novo mesto, Slovenia
3. Celje General Hospital, Department of Otorhinolaryngology, Oblakova 5, 3000 Celje, Slovenia
4. Community Health Centre dr. Adolfa Drolca Maribor, Ulica talcev 9, 2000 Maribor, Slovenia
5. Kemofarmacija d.d., Cesta na Brdo 100, 1000 Ljubljana, Slovenia
6. Zavod Zdravje d.o.o, Ulica padlih borcev 22, 6258 Prestranek, Slovenia