To a problem of introduction of local coordinates in a neighbourhood of an invariant toroidal set. Neliniini Kolyvannya, [S. l.], v. 4, n. 2, p. 171–189, 2001. Disponível em: https://twinhead.imath.kiev.ua/index.php/nosc/article/view/163. Acesso em: 22 jan. 2026.