PRZYBYŁA, Maciej J. Superstability of the d’Alembert functional equation in L_p^+ spaces. Annales Mathematicae Silesianae, [S. l.], v. 18, p. 39–47, 2004. Disponível em: https://trrest.vot.pl/ojsus/index.php/AMSIL/article/view/14090. Acesso em: 7 may. 2025.