DITCHEV, A. On the effective enumerations of partial structures. Ann. Sofia Univ. Fac. Math. and Inf., [S. l.], v. 83, n. 1, p. 29–37, 1992. Disponível em: https://ftl5.uni-sofia.bg/index.php/fmi/article/view/482. Acesso em: 5 dec. 2024.