1. Department of Otorhinolaryngology; Academic Medical Centre; Amsterdam the Netherlands
2. Department of Otorhinolaryngology; University of Crete School of Medicine; Heraklio Crete Greece
3. Department of Otorhinolaryngology; University Hospital Ulm; Ulm Germany
4. Department of Otorhinolaryngology and Head & Neck Surgery; Queens Medical Centre; Nottingham University Hospitals; Nottingham UK