1. Division of Gastroenterology and Hepatology, Weill Cornell Medical College, New York, New York, USA
2. Gastroenterology Department, Hospital Universitario Rio Hortega, Valladolid, Spain
3. Paul May and Frank Stein Interventional Endoscopy Center, California Pacific Medical Center, San Francisco, California, USA
4. Division of Gastroenterology and Hepatology, UNC School of Medicine, Chapel Hill, North Carolina, USA