1. S. Coleman, Phys. Rev. D15 (1977), 2929.
2. C. Callan and S. Coleman, Phys. Rev. D16 (1977), 1762.
3. See e.g. S. Weinberg, Phys. Rev. Letters 37 (1976), 657–
4. S. Weinberg, Phys. Rev. Letters 19 (1967), 1264.
5. S. Weinberg, Phys. Rev. Letters 19 (1967), 1264. A. Salam, Elementary Particle Theory, ed. by N. Svartholm (Stockholm, 1968)