ELQORACHI, Elhoucien; REDOUANI, Ahmed. Solutions and stability of generalized Kannappan’s and Van Vleck’s functional equations. Annales Mathematicae Silesianae, [S. l.], v. 32, p. 169–200, 2017. Disponível em: https://journals.us.edu.pl/index.php/AMSIL/article/view/13919. Acesso em: 8 apr. 2025.