1. For a rather complete list of references, see,e.g.,W. Kummer:Fort. d. Phys.,14, 429 (1966);L. Van Hove:Lectures at Scottish Universities' Summer School, 1966; CERN preprint TH. 676.
2. See,e.g.,R. H. Dalitz:Symmetries and the strong interactions, inProceedings of the XIII International Conference on High Energy Physics, Berkeley, 1966;F. Scheck:Proceedings of the NATO Summer School, Istanbul, August 1966.
3. A. Bialas, A. Gula, B. Muryn andK. Zalewski: Series of preprints from Jagellonian University, Cracow.
4. J. J. J. Kokkedee andL. Van Hove:Nuovo Cimento,42 A, 711 (1966);J. J. J. Kokkedee:Phys. Lett.,22, 88 (1966).
5. P. G. O. Freund:Phys. Rev. Lett.,15, 929 (1965);Nuovo Cimento,43 A, 1171 (1966).