1. H. Wielandt, “Vertauschbare nachinvariante Untergruppen,”Abh. Math. Sem. Univ. Hamburg,21, Nos. 1–2, 55–62 (1957).
2. J. C. Lennox and S. E. Stonehewer,Subnormal Subgroups of Groups, Clarendon, Oxford (1987).
3. H. Wielandt, “Über das Erzeignis paarwise kosubnormaler Untergruppen,”Arch. Math.,35, Nos. 1–2, 1–7 (1980).
4. S. F. Kamornikov, “Permutable subnormal subgroups of finite groups,”Dokl. Akad. Nauk BSSR,33, No. 5, 396–399 (1989).
5. S. F. Kamornikov, “Some properties of the formation of quasinilpotent groups,”Mat. Zametki,53, No. 2, 71–77 (1993).