1. Department of Otorhinolaryngology/Head and Neck Surgery; University Medical Center Groningen, University of Groningen; Groningen the Netherlands
2. Cancer Research Center; University of Groningen; Groningen the Netherlands
3. Groningen Papilloma Studies; University of Groningen; the Netherlands
4. Department of Otorhinolaryngology-Head and Neck Surgery; University of Helsinki, Helsinki University Hospital; Helsinki Finland
5. Wenckebach Institute; University of Groningen, University Medical Center Groningen; Groningen the Netherlands