1. Dashen,R.F., Gell-Mann,M.: Proceedings of the 3rd Coral Gables Conference on Symmetry Principles at High Energy, San Francisco: W. H. Freeman and Co.: 1966.
2. Fubini,S.: Nuovo Cimento 34A, 475 (1966).
3. Furlan,G.: this volume p. 118–147.
4. Bardakci,K., Segre,G.: Phys. Rev. 153, 1263 (1967).
5. Jersak,J., Stern,J.: Nuovo Cimento 59, 315 (1969).