1. Connes, A.,Publ. IHES 62, 257 (1986).
2. Connes, A.Geometrie noncommutative Inter Editions, Paris, 1990.
3. Dubois-Violette, M.,C.R. Acad. Sci. Paris Ser. I,307, 403 (1988).
4. Madore, J., Lectures on noncommutative geometry, Orsay preprint, January 1993.
5. Madore, J.,J. Math. Phys. 32, 332 (1991).