1. A. I. Mal'tsev, Algebraic Systems [in Russian], Nauka (1970).
2. Yu. L. Ershov, E. A. Palyutin, and M. A. Taitslin, Mathematical Logic [in Russian], Novosibirsk State Univ. (1973).
3. A. I. Abakumov, E. A. Palyutin, M. A. Taitslin, and Yu. E. Shishmarev, "Categorical quasivarieties," Algebra Logika,11, No. 1, 3–38 (1972).
4. E. A. Palyutin, "On complete quasivarieties," Algebra Logika,11, No. 6, 689–693 (1972).
5. E. A. Palyutin, "On categorical quasivarieties of arbitrary signature," Sib. Mat. Zh.,14, No. 6, 1285–1303 (1973).