1. Bala, P., Carter, R. W.: Classes of unipotent elements of simple algebraic groups. To appear.
2. Benard, M.: On the Schur indices of characters of the exceptional Weyl groups. Ann. of Math.94, 89–107 (1971)
3. Borel, A.: Linear algebraic groups, New York: Benjamin 1969
4. Borel, A., Tits, J.: Groupes réductifs. Publ. Math. I.H.E.S.27, 55–150 (1965)
5. Brieskorn, E.: Singular elements of semi-simple algebraic groups. Proc. Int. Congress Math., Nice (1970)