Akkaoui, Ahmed, and Brahim Fadli. “New Results about Quadratic Functional Equation on Semigroups”. Annales Mathematicae Silesianae 39, no. 2 (November 19, 2024): 209–222. Accessed December 5, 2025. https://journals.us.edu.pl/index.php/AMSIL/article/view/18119.