Nilpotent Fixed Point Free Automorhism Group of Solvable Groups. Thomas R. Berger — 1973 Mathematische Zeitschrift
More Normal Fitting Classes of Finite Solvable Groups. Thomas R. Berger — 1976 Mathematische Zeitschrift
An Example in the Theory of Normal Fitting Classes. Thomas R. Berger; John Cossey — 1977 Mathematische Zeitschrift