1. P. Federbush:Phys. Rev.,121, 1247 (1961).
2. A. S. Wightman: inCargèse Lectures in Theoretical Physics, edited byM. Lévy (New York, N. Y., 1964), p. 171.
3. K. Hepp:Comm. Math. Phys.,2, 301 (1966), eqs. (1.7)-(1.9).
4. N. Bogoliubov andD. Shirkov:Introduction to the Theory of Quantized Fields (New York, N. Y., 1959).