Mansouri, B., A. Ardjouni, and A. Djoudi. “Periodicity and Stability in Neutral Nonlinear Differential Equations by Krasnoselskii‘s Fixed Point Theorem”. CUBO, A Mathematical Journal, vol. 19, no. 3, Oct. 2017, pp. 15–29, doi:10.4067/S0719-06462017000300015.