MARCHUK, N. A.; TEPLINSKY, Yu. V. On the Smoothness of the Invariant Torus of a Countable System of Difference Equations with Parameters. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 53, n. 9, p. 1241–1250, 2001. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/4343. Acesso em: 6 dec. 2025.