BÉZIAU, J.-Y. Logic may be simple. Logic, congruence and algebra. Logic and Logical Philosophy, [S. l.], v. 5, n. 5, p. 129–147, 2003. DOI: 10.12775/LLP.1997.009. Disponível em: https://apcz.umk.pl/LLP/article/view/LLP.1997.009. Acesso em: 6 dec. 2021.