1. R. Gatto andG. Sartori:Nuovo Cimento,30 A, 430 (1975).
2. R. F. Streater andA. S. Wightman:PCT, Spin and Statistics and All That (New York, N. Y., 1964).
3. M. Guenin andG. Velo:Helv. Phys. Acta,41, 362 (1961).
4. It has been shown byHepp (5) that, after smoothing by test function, the perturbation series converges strongly.
5. R. Hepp:Théorie de la renormalization, inLecture Notes in Physics (Berlin, 1969).