TINCHEV, T.; YANCHEV, M. MODAL OPERATORS FOR RATIONAL GRADING. Ann. Sofia Univ. Fac. Math. and Inf., [S. l.], v. 100, p. 47–66, 2011. Disponível em: https://ftl5.uni-sofia.bg/index.php/fmi/article/view/246. Acesso em: 21 nov. 2024.