1. Borel, A.: Linear algebraic groups. New York: Benjamin 1969
2. Vinberg, E.B.: Rings of definition of dense subgroups of semi-simple linear groups. Math. USSR Izvestija5, 45?55 (1971)
3. Proc. Symp. Pure Math.;H. Furstenberg,1973
4. Furstenberg, H.: Equivariant measurable maps and representations of lattice subgroups. Preprint
5. Mostow, G.D.: Intersection of discrete subgroups with Cartan subgroups. J. Indian Math. Soc.34, 203?214 (1970)