LYKOVA, O. B. On properties of central manifolds of a stationary point. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 49, n. 1, p. 68–76, 1997. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/4987. Acesso em: 5 dec. 2025.