1. For a summary of ideas and results seee.g. M. Jacob:Lectures Given at the VIII Internationale Universitätswochen für Kernphysik der Universität Graz, Schladming, 1969. CERN Th. 1010; andTheory of hadronic interactions, Rapporteur's talk at the Lund International Conference on Elementary Particles, Lund, 1969.
2. L. Van Hove:Phys. Lett.,24 B, 183 (1967);L. Durand III:Phys. Rev.,161, 1610 (1967).
3. G. Veneziano:Nuovo Cimento,57 A, 190 (1968).
4. C. Lovelace:Phys. Lett.,28 B, 264 (1968);J. Shapiro andJ. Yellin: UCRL 18500 (1968).
5. H. Harari:Phys. Rev. Lett.,22, 562 (1969);J. L. Rosner:Phys. Rev. Lett.,22, 689 (1969).