PARASYUK, I. O. Reduction and coisotropic invariant tori of Hamiltonian systems with non-poisson commutative symmetries. I. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 46, n. 5, p. 537–544, 1994. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/5717. Acesso em: 5 dec. 2025.