1. Dashen, R. F., and Sharp, D. H., Phys. Rev., 165, 1857 (1968).
2. Sharp, D. H., Phys. Rev., 165, 1867 (1968).
3. Callan, C. G., Dashen, R. F., and Sharp, D. H., Phys. Rev., 165, 1883 (1968).
4. Sugawara, H., Phys. Rev., 170, 1659 (1968).
5. The presentation of the material in the first half of this section follows S. L. Adler and R. F. Dashen, Chapter I in
Current Algebras, Benjamin, N. Y., (1968). For further background material one can consult other chapters in the Adler-Dashen book as well as B. Renner, Current Algebras and Their Applications, Pergamon, N. Y., (1968), and the lectures of L. Michel and L. O'Raifeartaigh in these Proceedings.