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://trrest.vot.pl/ojsus/index.php/AMSIL/article/view/14210. Acesso em: 8 may. 2025.