A. Fahad, M., and H. H. . Khamees. “Effect of Vitamin D, C and Selenium Intake on Disease Severity and Outcomes in Patients COVID-19”. Scholastic: Journal of Natural and Medical Education, vol. 2, no. 5, May 2023, pp. 1-9, https://univerpubl.com/index.php/scholastic/article/view/1328.