Optimal Morse – Smale flows with singularities on the boundary of surface. Neliniini Kolyvannya, [S. l.], v. 21, n. 2, p. 231–237, 2018. Disponível em: https://twinhead.imath.kiev.ua/index.php/nosc/article/view/906. Acesso em: 21 jan. 2026.