Kannan, Dharshini, et al. “Analysis of Potential Risk Factors of COVID-19 Based on Variants: Omicron, Delta, and Alpha”. Archives of Clinical and Biomedical Research, vol. 7, no. 6, Nov. 2023, pp. 590-03, https://fortunejournals.org/ojs/index.php/acbr/article/view/15043.