Rossiyah, Nella. “ASSOCIATION OF VITAMIN D DEFICIENCY TO SEVERITY OF COVID-19 : A SYSTEMATIC REVIEW”. Journal of Advanced Research in Medical and Health Science (ISSN 2208-2425) 9, no. 3 (March 24, 2023): 80–84. Accessed September 12, 2025. https://textitlejournal.com/nnpub.org/index.php/MHS/article/view/1617.