1. Metric automorphisms with quasi-discrete spectrum;Abramov, L. M.;Izv. Akad. Nauk SSSR Ser. Mat.,1962
2. Minimal dynamical systems with quasi-discrete spectrum;Hahn, Frank;J. London Math. Soc.,1965
3. Some characteristic properties of dynamical systems with quasi-discrete spectra;Hahn, Frank;Math. Systems Theory,1968
4. Publications of the Mathematical Society of Japan;Halmos, Paul R.,1956
5. A. Kuroš, Theory of groups, GITTL, Moscow, 1953; English transl. of 2nd ed., Vol. I, Chelsea, New York, 1955. MR 15, 501; 17, 124.