NIKOLOVA, S. $\prod_{1}^{0}$-POSITIVE INDUCTIVE DEFINABILITY ON ABSTRACT STRUCTURES. Ann. Sofia Univ. Fac. Math. and Inf., [S. l.], v. 90, p. 91–108, 1998. Disponível em: https://admin.uni-sofia.bg/index.php/fmi/article/view/288. Acesso em: 23 jan. 2025.