NIKODEM, Kazimierz. The stability of the Pexider equation. Annales Mathematicae Silesianae, [S. l.], v. 5, p. 91–93, 1991. Disponível em: https://journals.us.edu.pl/index.php/AMSIL/article/view/14286. Acesso em: 18 apr. 2025.