1. Faculty of Dentistry, Institute of Oral Biology University of Oslo Oslo Norway
2. Department of Pathology, Rikshospitalet Oslo University Hospital Oslo Norway
3. Department of Otorhinolaryngology University Hospital of North Norway Tromsø Norway
4. Department of Medical Biology, Faculty of Health Sciences UiT The Arctic University of Norway Tromsø Norway
5. Department of Pathology Aarhus University Hospital Aarhus Denmark