1. A. I. Budkin, ?Independent axiomatizability of quasivarieties of groups,? Mat. Zametki,31, No. 6, 817?825 (1982).
2. A. I. Budkin, ?Independent axiomatizability of quasivarieties of groups,? in: Abstracts of Reports, XVIII All-Union Algebra Conference, Kishinev (1985).
3. A. Gorbunov, ?Covers in lattices of quasivarieties and independent axiomatizability,?Algebra Logika,16, No. 5, 505?548 (1977).
4. B. L. van der Waerden, Algebra [Russian translation], Nauka, Moscow (1979).