1. Wreath products and p-groups;Baumslag,1959
2. The upper central series in soluble groups;Gruenberg;Illinois J. Math.,1961
3. The hypercenter of linear groups;Gruenberg;J. Algebra,1968
4. Finiteness conditions for soluble groups;Hall,1954
5. P. Hall, “Canadian Notes, 1957,” Queen Mary College, London.