1. Division of Gastroenterology, Department of Internal Medicine, CGH Medical Center, 100 East Le Fevre Road, Sterling, IL 61081, USA
2. Division of Gastroenterology, Department of Internal Medicine, Saint Francis Hospital, 355 Ridge Avenue, Evanston, IL 60202, USA
3. Division of Gastroenterology, Department of Internal Medicine, University of Tishreen, Aleppo Street, P.O. Box 2230, Latakia, Syria
4. Department of Mathematics and Computer Science, Augusta State University, 2500 Walton Way, Augusta, GA 30904, USA