1. Cf. CERN-Columbia-Rockfeller Collaboration:Proceedings of the XVI International Conference on High-Energy Physics, Chicago-Batavia, 1972 (to be published).
2. See,e.g.,D. Cline, F. Halzen andM. Waldrop: Wisconsin preprint (1973).
3. G. Domokos andS. Kövesi-Domokos:Nuovo Cimento,14 A, 667 (1973)
4. This has been particularly emphasized inG. Domokos, S. Kövesi-Domokos andE. Schonberg:Fields and Quanta,3, 165 (1972).
5. Cf.,G. Mack:Kaiserslautern Lectures (1972);