1. A. G. Kurosh and S. N. Chernikov, Solvable and nilpotent groups, Usp. Matem. Nauk.2, No. 3, 18?59 (1947).
2. M. Z. Kargapolov. Locally finite groups possessing normal systems with finite factors. Sib. Matem. Zh.2, No. 6, 853?873 (1961).
3. M. I. Kargapolov, About a problem of O. Yu. Shmidt, Sib. Matem. Zh.,4, No. 1, 232?235 (1963).
4. A. G. Kurosh, Theory of groups [in Russian], Gostekhizdat. Moscow (1953).
5. S. N. Chernikov. About the centralizer of a complete abelian normal divisor of an infinite and periodic group. Dokl. Ak. Nauk SSSR,72, No. 2, 243?246 (1950).