1. Internal Medicine – Gastroenterology and Hepatology, Berufsgenossenschaftliche Universitätsklinik Bergmannsheil GmbH, Bochum, Germany
2. Interdisciplinary Endoscopy, University Hospital Hamburg-Eppendorf, Hamburg, Germany
3. Internal Medicine, Knappschaftkrankenhaus Bochum-Langendreer, Bochum, Germany