1. Baylor University Medical Center; Texas A&M University; Dallas Texas USA
2. Mayo Clinic; Rochester Minnesota USA
3. Nottingham Digestive Diseases Centre; Queens Medical Centre; Nottingham UK
4. University of Chicago; Chicago Illinois USA
5. University of Washington; Seattle Washington USA
6. University of Cincinnati; Cincinnati Ohio USA
7. Medical University of Graz; Graz Austria
8. University of Sussex; Brighton UK
9. Baylor College of Medicine; Houston Texas USA