1. Characters and derived length in groups of odd order;Berger;J. Algebra,1976
2. Group Representation Theory (Parts A, B);Dornhoff,1971
3. The Representation Theory of Finite Groups;Feit,1982
4. On Groups with a Small Number of Character Degrees;Garrison,1973
5. The p-length of a p-soluble group and reduction theorems for Burnside's problem;Hall,1956