1. Many excellent reviews are available in the literature. See e.g. K. Gottfried in Proceedings of the 1977 International Symposium on Lepton and Photon Interactions at High Energies. Hamburg, F. Gutbrod, ed. (DESY, Hamburg (1978.) C. Quigg, J.L. Rosner: Phys. Rep56, 167 (1979);
2. H. Grosse, A. Martin. Phys. Rep.60, 343 (1980)
3. E. Eichten et al.: Phys. Rev.D21, 203 (1980)
4. A. Martin; Phys. Lett.93B, 338 (1980)
5. M. Krammer, P. Leal-Ferreira: Rev. Bras. Fis.6, 7 (1976)