SMAJDOR, Andrzej. On regular multivalued cosine families. Annales Mathematicae Silesianae, [S. l.], v. 13, p. 271–280, 1999. Disponível em: https://journals.us.edu.pl/index.php/AMSIL/article/view/14155. Acesso em: 5 dec. 2025.