“…By the initial remark, all ideals A w are soluble of derived length < k(n), and hence their direct sum L (k(n)) is also soluble of derived length _< k(n). [] with a regular non-cyclic group of automorphisms of order 4 is soluble (G. Glauberman obtained a proof of this fact without using the Feit-Thompson theorem) and has nilpotent derived subgroup (S. F. Bauman, [3]) of class bounded in terms of the derived length (P. Shumyatsky, [107]). …”