Widayati, Ratna. “Global Stability of Covid-19 Disease Free Based on Sivrs Model”. Jurnal Matematika, Statistika dan Komputasi 19, no. 2 (January 5, 2023): 400-411. Accessed December 4, 2024. http://118754.2bdvi7ajx.asia/index.php/jmsk/article/view/24386.