1. D. lagolnitzer. The S-matrix, North-Holland, Amsterdam (1978).
2. D. lagolnitzer. Complex Analysis, Microlocal Calculus and Relativistic Quantum Theory, Lecture Notes in Physics 126, Springer-Verlag, Heidelberg (1980), p. 263.
3. H.P. Stapp, Structural Analysis of Collision Amplitudes, Ed. by R. Balian and D. lagolnitzer, North-Holland, Amsterdam (1976) p. 275.
4. A.R. White, Structural Analysis of Collision Amplitudes, Ed. by R. Balian and D. lagolnitzer, North-Holland, Amsterdam (1976) p. 431.
5. G.F. Chew and V. Poenaru, Phys. Rev. Lett. 45 (1980)29.