LAGODA, V. A.; PARASYUK, I. O. Theorem on the existence of an invariant section over $\mathbb{R}^m$ for the indefinite monotone system in $\mathbb{R}^m \times \mathbb{R}^n$. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 65, n. 1, p. 103–118, 2013. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/2407. Acesso em: 5 dec. 2025.