1. C. G.Chang and H. J.Keisler, Model Theory. Stud. Logic 73, Amsterdam-New York 1973.
2. J. L. Dyer, On the isomorphism problem for polycyclic groups. Math. Z.112, 145?153 (1969).
3. P. Hall, Finiteness conditions for soluble groups. Proc. London Math. Soc. (3)4, 419?436 (1954).
4. P. Hall, On the finiteness of certain soluble groups. Proc. London Math. Soc. (3)9, 595?622 (1959).
5. I. Kaplansky, Infinite Abelian Groups. Second edition, University of Michigan Press, Ann Arbor 1969.