1. W. Feit,The current situation in the theory of finite simple groups, Actes Congress Intern. Math. (1970), Tome 1, 55–93.
2. D. Gorenstein,Finite groups, Chapters 16 and 17, Harper and Row, New York, 1968.
3. D. Gorenstein,Centralizers of involutions in finite simple groups, Chapter II of Simple Groups, Academic Press, New York, 1971.