FRANCIS, A.; AKYENYI, A. S.; ITOPA, A. S. Analysis of a modified Covid-19 model in Nigeria and approximations using differential transformation method. Dutse Journal of Pure and Applied Sciences, [S. l.], v. 8, n. 2b, p. 170–183, 2022. DOI: 10.4314/dujopas.v8i2b.17. Disponível em: https://www.ajol.info/index.php/dujopas/article/view/227298. Acesso em: 6 nov. 2026.