ARDJOUNI, A.; DJOUDI, A. EXISTENCE OF POSITIVE PERIODIC SOLUTIONS FOR A NONLINEAR NEUTRAL DIFFERENCE EQUATION WITH VARIABLE DELAY. Journal of Nonlinear Analysis and Optimization: Theory & Applications (JNAO), [S. l.], v. 4, n. 2, p. 31–38, 2013. Disponível em: https://ph03.tci-thaijo.org/index.php/jnao/article/view/2700. Acesso em: 2 sep. 2026.