FORTI, Gian Luigi. Stability of functional equations and properties of groups. Annales Mathematicae Silesianae, [S. l.], v. 33, p. 77–96, 2019. Disponível em: https://journals.us.edu.pl/index.php/AMSIL/article/view/13652. Acesso em: 8 apr. 2025.