KHALAF-ALLAH, R. Asymptotic behavior and periodic nature of two difference equations. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 61, n. 6, p. 834–838, 2009. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/3061. Acesso em: 5 dec. 2025.