1. See,e.g.,N. N. Bogolubov andD. Shirkov:Introduction to the Theory of Quantized Fields (New York, N. Y., 1979);K. Symanzik:Lagrangian quantum field theory, Internal Bericht, DESY T-71-1;C. Itzykson andJ. B. Zuber:Quantum Field Theory (New York, N. Y., 1980).
2. L. D. Landau andI. M. Khalatnikov:Ž. Ėksp. Teor. Fiz.,2, 69 (1956);K. Johnson andB. Zumino:Phys. Rev. Lett.,3, 351 (1959);B. Zumino:J. Math. Phys. (N. Y.),1, 1 (1960).
3. H. Hertz:Ann. Phys. (Leipzig),36, 1 (1886).
4. D. Zwanziger:Phys. Rev. D,19, 3614, (1979).
5. E. d’Emilio andM. Mintchev:The asymptotic limit for the electron field in QED, Pisa IFUP preprint;Physical charged sectors in QED.—I:Infra-Red asymptotics, Pisa IFUP preprint.