1. A. I. Budkin and V. A. Gorbunov, "Towards a theory of quasivarieties of algebraic systems," Algebra i Logika,14, No. 2, 123–142 (1975).
2. M. I. Kargapolov and Yu. I. Merzlyakov, Foundations of Group Theory [in Russian], Nauka (1972).
3. A. I. Mal'tsev, Algebraic Systems [in Russian], Nauka (1970).
4. A. I. Mal'tsev, Algorithms and Recursive Functions [in Russian], Nauka (1965).
5. A. I. Mal'tsev, "Some boundary questions in algebra and mathematical logic," in: Proceedings of the International Mathematics Congress, Moscow, 1966, Mir (1968), pp. 217–231.