1. See, for example,S. L. Adler andR. T. Dashen:Current Algebra and Applications to Particle Physics (New York, 1968).
2. S. L. Adler:Phys. Rev.,140, B 736 (1965);W. Weisberger:Phys. Rev.,143, 1302 (1966).
3. N. Cabibbo andL. A. Radicati:Phys. Lett.,19, 697 (1966);R. F. Dashen andM. Gell-Mann: inProceedings of the Third Coral Gables Conference on Symmetry Principles at High Energy (San Francisco, Cal., 1966).
4. S. Fubini:Nuovo Cimento,43 A, 475 (1966);R. F. Dashen andM. Gell-Mann: inProceedings of the Third Coral Gables Conference on Symmetry Principles at High Energy (San Francisco, Cal., 1966).
5. For (conserved) vector currents, it can be shown that seagull terms and Schwinger terms cancel, and one has the usual Ward identity (e.g. eq. (2.3)), seeS. L. Adler andR. F. Dashen:Current Algebra, Chap. 3, Appendix B (New York, 1968);L. S. Brown:Phys. Rev.,150, 1338 (1966).