TKACH, B. P. Conditional stability of quasitoroidal manifolds of systems of partial differential equations. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 50, n. 3, p. 401–408, 1998. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/4939. Acesso em: 5 dec. 2025.