GEBERT, Holger. A direct proof of a theorem of K. Baron. Annales Mathematicae Silesianae, [S. l.], v. 9, p. 101–103, 1995. Disponível em: https://journals.us.edu.pl/index.php/AMSIL/article/view/14210. Acesso em: 5 dec. 2025.