An Seir Model for Measles Transmission in North Sumatra Using the Fourth-Order Runge–Kutta Method for an Optimal Control Strategy. Proximal: Jurnal Penelitian Matematika dan Pendidikan Matematika, [S. l.], v. 9, n. 2, p. 696–708, 2026. DOI: 10.30605/proximal.v9i2.9552. Disponível em: https://e-journal.my.id/proximal/article/view/9552. Acesso em: 19 aug. 2026.