1. V. A. Shcherbina, Teor. Mat. Fiz.14, 342 (1973).
2. V. D. Gordevskii, System of Equations for Vertex Functions of the Chronological Exponential (Spinor Theories), Paper No. 2728-75 DEP deposited with VINITI (All-Union Institute of Scientific and Technical Information) (1975).
3. E. S. Fradkin, Zh. Eksp. Teor. Fiz.,29, 121 (1955).
4. E. S. Fradkin, Zh. Eksp. Teor. Fiz.,28, 750 (1956).
5. E. S. Fradkin, Zh. Eksp. Teor. Fiz.,26, 751 (1954).