PELYUKH, G. P. On periodic solutions of nonlinear difference equations in the critical case. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 50, n. 2, p. 304–308, 1998. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/4964. Acesso em: 17 apr. 2025.