Galois coverings and the problem of axiomatization of the representation type of algebras. Stanislaw Kasjan, José Antonio de la Peña (2005) Extracta Mathematicae
Generalization of the concept of variety and quasivariety to partial algebras through category theory [Book] H. Andréka, I. Németi (1983)
Gödel's diagonalization technique and related properties of theories A. Macintyre, H. Simmons (1973) Colloquium Mathematicae
Groupes nilpotents existentiellement clos de classe fixée Wilfrid Hodges (1984) Mémoires de la Société Mathématique de France