1. For a recent review see,e.g.,G. Altarelli, CERN-TH. 6867/93.
2. A. J. Buras, J. Ellis, M. K. Gaillard andD. V. Nanopoulos:Nucl. Phys. B,135, 66 (1978);D. V. Nanopoulos andD. A. Ross:Nucl. Phys. B,157, 273 (1979);Phys. Lett. B,108, 351 (1982) andPhys. Lett. B,118, 99 (1982).
3. For reviews see,e.g.,R. Arnowitt andP. Nath:Applied N=1 Supergravity (World Scientific, Singapore 1983);H. P. Nilles:Phys. Rep.,110, 1 (1984).
4. For a recent review seeJ. L. Lopez, D. V. Nanopoulos andA. Zichichi, CERN-TH. 6926/93 and Texas A&M University preprint CTP-TAMU-33/93.
5. H. Georgi andS. Glashow:Phys. Rev. Lett.,32, 438 (1974).