ŠLAPAL, Josef. Categories of universal algebras in which direct products are tensor products. Annales Mathematicae Silesianae, [S. l.], v. 9, p. 7–10, 1995. Disponível em: https://journals.us.edu.pl/index.php/AMSIL/article/view/14199. Acesso em: 5 dec. 2025.