CHOBANOV, I. INTRODUCTION TO AN ALGEBRAIC THEORY OF ARROWS, III. Ann. Sofia Univ. Fac. Math. and Inf., [S. l.], v. 82, n. 1, p. 127–172, 1991. Disponível em: https://admin.uni-sofia.bg/index.php/fmi/article/view/525. Acesso em: 16 jan. 2025.