1. H. Moreno and H.N. Fried, Nice Preprint NTH 77/5.
2. H. Cheng and T.T.Wu, Phys.Rev.Letters 24, 1455 (1970); S-J Chang and T-M Yan, Phys.Rev. D4, 537 (1971).
3. Rather extensive discussions and applications of the fundamental Bloch-Nordsieck approximation may be found in: H.M. FRIED, “Functional Methods and Models in Quantum Field Theory”, M.I.T. Press, Cambridge (1972).
4. R. Blankenbecler and H.M. Fried, Phys. Rev. D8, 678 (1973).
5. M. Levy and J. Sucher, Phys. Rev. D2, 1716 (1970).