MITROPOLSKY , Yu. A.; LOPATIN , A. K. Asymptotic decomposition of fully integrable Pfaff systems with perturbation. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 40, n. 3, p. 349–356, 1988. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/9148. Acesso em: 7 dec. 2025.