Elazzouzi, A., Ezzinbi, K. and Kriche, M. 2021. On the periodic solutions for some retarded partial differential equations by the use of semi-Fredholm operators. CUBO, A Mathematical Journal. 23, 3 (Dec. 2021), 469–487. DOI:https://doi.org/10.4067/S0719-06462021000300469.