ŁUKASIK, Radosław. A functional equation with biadditive functions. Annales Mathematicae Silesianae, [S. l.], v. 36, n. 2, p. 193–205, 2022. Disponível em: https://journals.us.edu.pl/index.php/AMSIL/article/view/13591. Acesso em: 5 dec. 2025.