Optimum Control of SEIR Model on COVID-19 Spread with Delay Time and Vaccination Effect in South Sulawesi Province. Jurnal Varian, [S. l.], v. 6, n. 1, p. 11–24, 2022. DOI: 10.30812/varian.v6i1.1882. Disponível em: https://journal.universitasbumigora.ac.id/Varian/article/view/1882. Acesso em: 1 jul. 2025.