KURBANSHOEV , S. Z. On behaviour of integral curves in the vicinities of optimal integral varieties. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 44, n. 8, p. 1049–1060, 1992. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/8033. Acesso em: 5 dec. 2025.