Lecture Notes in Physics Edited by J. Ehlers, Mijnchen, K. Hepp, Zijrich R. Kippenhahn, Mi.inchen, H. A. Weidenmtiller, Heidelberg and J. Zittat-tz, Kijln Managing Editor: W. Beiglbijck, Heidelberg 80 Mathematical Problems in Theoretical Physics International Conference Held in Rome, June 6-15,1977 Edited by G. Dell’Antonio, S. Doplicher and G. Jona-Lasinio Springer-Verlag Berlin Heidelberg New York 1978