DITCHEV, A. Effective enumerations of families of recursive functions. Ann. Sofia Univ. Fac. Math. and Inf., [S. l.], v. 93, p. 31–37, 2001. Disponível em: https://annual.uni-sofia.bg/index.php/fmi/article/view/200. Acesso em: 13 apr. 2025.