SMAJDOR, Andrzej. On a functional equation. Annales Mathematicae Silesianae, [S. l.], v. 8, p. 217–226, 1994. Disponível em: https://trrest.vot.pl/ojsus/index.php/AMSIL/article/view/14237. Acesso em: 7 may. 2025.