1. A. Klein andC. Zemach:Phys. Rev.,108, 126 (1957).
2. W. Zimmermann:Nuovo Cimento,10, 597 (1959);R. Blankenbecler:Nucl. Phys.,135, 97 (1959).
3. C. Lovelace:Phys. Rev.,135, B 1225 (1964).
4. E. O. Alt, P. Grassberger andW. Sandhas: University of Bonn, preprint 2–16, November 1966.
5. L. D. Faddeev:Žurn. Ėksp. Teor. Fiz.,39, 1459 (1960), English translation,Sor. Phys. JETP,12, 1014 (1961).