AKHMETOV, M. U. On the smoothness of solutions of differential equations with a discontinuous right-hand side. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 45, n. 12, p. 1587–1594, 1993. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/5965. Acesso em: 7 apr. 2025.