1. Rush University Medical Center and Advanced Center for Specialty Care, Advocate Illinois Masonic Medical Center; Chicago Illinois U.S.A.
2. ENT and Allergy Associates; Orange Regional Medical Center; Middletown New York U.S.A.
3. Head and Neck Department; St. Joseph Hospital; Bremen Germany
4. Department of Cardiology; Center of Sleep Medicine, Charité-Universitätsmedizin Berlin; Berlin Germany
5. Saint Luc University Clinics; Department of Oto-Rhino-Laryngology; Institute of Neurosciences; University of Louvain; Brussels Belgium
6. Colorado Head and Neck Specialists; Denver Colorado U.S.A.
7. Mannheim University ENT Clinic; Mannheim Germany