1. B. Plotkin,Algebraic logic, varieties of algebras and algebraic varieties, inProceedings of the International Algebra Conference, St. Petersburg, 1995, Walter de Gruyter, New York and London, 1996, to appear.
2. B. Plotkin.Categories of algebraic varieties, to appear.
3. L. Fuchs,Infinite Abelian Groups, Academic Presss, New York and London, 1970.
4. Jan Shi-Jain,Linear groups over a ring, Chinese Mathematics7, No. 2 (1965), 163–179.
5. P. Cohn,Universal Algebra, Harper & Row, New York, Evanston and London, 1965.