1. Division of Gastroenterology Center for Esophageal Diseases University of California San Diego La Jolla CA USA
2. Department of Medicine Feinberg School of Medicine Northwestern University Chicago Illinois USA
3. Department of Gastroenterology and Hepatology University Hospital Zürich Zürich Switzerland
4. Digestive Function: Basel Laboratory and Clinic for Motility Disorders and Functional Digestive Diseases Klinik Arlesheim Arlesheim Schweiz
5. Department of Gastroenterology and Hepatology Amsterdam University Medical Center Amsterdam The Netherlands