1. P. Gravel etC. Gauthier:Class. Q. Grav.,4, 101 (1987).
2. P. Gravel etC. Gauthier:Nuovo Cimento A,100, 661 (1988).
3. J. A. Wolf:Spaces of Constant Curvature (Publish or Perish, Boston, Mass., 1974).
4. M. J. Duff, B. E. W. Nilsson etC. N. Pope:Phys. Rep.,130, 1 (1986).
5. C. Wetterich:Fermion chirality from higher dimensions and Kaluza-Klein theories with noncompact internal space, dansPhysics in Higher Dimensions, Proceedings of the 2nd Jerusalem Winter School for Theoretical Physics, éd.T. Piran etS. Weinberg (World Scientific, Singapore, 1986), p. 205.