1. G. Zweig: inBaryon 1980. Proceedings of the IV International Conference on Baryon Resonances, edited byN. Isgur (Toronto, 1980), p. 439;M. Gell-Mann andY. Ne’eman:The Eightfold Way (New York, N.Y., 1964).
2. An excellent review is to be found inV. de Alfaro, S. Fubini, G. FurlanandC. Rossetti:Currents in Hadron Physics (Amsterdam, 1973).
3. SeeR. Peccei: inParticle Physics 1980, edited byI. Andrić, I. Dadić andN. Zovko(Amsterdam, 1981), p. 209, and references therein.
4. G. Höhler inParticle Physics 1980, edited byI. Andrić, I. Dadić andN. Zovko, (Amsterdam, 1981), p. 343.
5. P. M. Gensini:Nuovo Cimento A,17, 557 (1973);Nuovo Cimento A,60, 234 (1980) and erratum,63, 256 (1981);Z. Phys. C,14, 319 (1982).