6. S. Kobayashi and K. Nomizu, Foundations of differential geometry, Interscience, New York, 1963. 7. C. C. Moore, Ergodicity of flows on homogeneous spaces, (to appear). 8. J. G. Sinaï, Proof of the ergodic hypothesis f or a dynamical system of statistical mechanics, Dokl. Akad. Nauk SSSR 153 (1963), 1261-1264=Soviet Math. Dokl. 4 (1963), 1818-1822. 9. I. Segal and J. von Neumann, A theorem on unitary representations of semisimple Lie groups, Ann. of Math. 52 (1950), 509-517. 10. T. Sherman, A weight theory for unitary representations, (to appear).