FECHNER, Włodzimierz. Separation theorems for conditional functional equations. Annales Mathematicae Silesianae, [S. l.], v. 21, p. 31–40, 2007. Disponível em: https://journals.us.edu.pl/index.php/AMSIL/article/view/14060. Acesso em: 5 dec. 2025.