1. Lect. Notes Math.;DM Arnold,1982
2. L. Fuchs, Infinite Abelian Groups, Vols. 1, 2, Academic Press (1970, 1973).
3. F. Kasch, Moduln und Ringe, Teubner, Stuttgart (1977).
4. P. A. Krylov, “Radicals of rings of endomorphisms of torsion-free Abelian groups,” Mat. Sb., 95, No. 10, 214–228 (1974).
5. R. S. Pierce, Associative Algebras, Springer, New York (1982).