COVID-19 and Upper Gastrointestinal Bleeding; Etiology, Risk Factors, and Outcomes: A Case-Control Study. - Shafieipour, Sara; Zadeh Rukerd, Mohammad Rezaei; Farsiu, Niloofar; Nakhaie, Mohsen; Jahangiri, Samaneh; Yousefi, Maysam; Mirkamali, Hanieh; Mohamadinezhad, Aryan (Middle East Journal of Digestive Diseases, 2025)