Gąsiorowska , A. (2021) “The gastrointestinal tract and COVID-19. Observations after the year of the pandemic. Part 1. Patients with diseases of the upper gastrointestinal tract”, Medycyna Faktow (J EBM), 14(3(52), pp. 225-231. doi: 10.24292/01.MF.0321.2.