1. Maschke,Mathematische Annalen 52 (1899), p. 363.
2. Maschke,American Journal of Mathematics 17 (1895), p. 168.
3. See Moore,Mathematische Annalen 50 (1898), p. 215 for proof and references.
4. Consult Burnside,Theory of Groups, Cambridge University Press, 1897; and Weber,Algebra, Bd II, Braunschweig (Vieweg und Sohn), 2nd edition, 1899.
5. Burnside,Theory of groups, pp. 371?375.