M. Al-Mekhlafi, S., A. Boudaoui, N. Laksaci, T. Abdeljawad, and B. Abdalla. “Modeling Dengue-COVID-19 Co-Epidemics via Crossover Discrete Time Systems With Variable-Order Fractional Memory”. Contemporary Mathematics, vol. 7, no. 4, July 2026, pp. 4111-62, doi:10.37256/cm.7420268949.