PARASYUK, I. O. Variables of the action-angle type on symplectic manifolds stratified by coisotropic tori. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 45, n. 1, p. 77–85, 1993. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/5785. Acesso em: 5 dec. 2025.