1. Center for Digestive Diseases, Internal Medicine Center Eppendorf, Hamburg
2. Center for Esophageal Disorders, University Hospital Eppendorf, Hamburg
3. Dept. of Gastroenterology, Hepatology and Infectiology, University Hospital Magdeburg
4. II. Medical Dept, Klinikum Rechts der Isar, Technical University, Munich
5. Medical Department II, Helios Hospital, Krefeld
6. Department of Internal Medicine, Siloah Hospital, Hannover
7. bng-Management, Ulm
8. Gastroenterologist in private practice, Saarlouis
9. Internal Medicine, Jung-Stilling-Hospital, Siegen