1. Department of Otorhinolaryngology–Head and Neck Surgery, University of Groningen, University Medical Center Groningen, Groningen, Netherlands
2. Cancer Research Center Groningen, University of Groningen, Groningen, Netherlands
3. Groningen Papilloma Studies, University Medical Center Groningen, Groningen, 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, Netherlands