1. G. Bhattacharyya, Nucl. Phys. (Proc. Suppl.) 52A (1997) 83; H. Dreiner, hep-ph/9707435, to be published in Perspectives on Supersymmetry, G. Kane (Ed.), World Scientific.
2. J.W.F. Valle, FTUV-98-18, hep-ph/9802292.
3. See, for example, P.H. Frampton, O.C.W. Kong, Phys. Rev. D 53 (1995) R2293
4. Phys. Rev. Lett. 77 (1996) 1699
5. O.C.W. Kong, UNC-CH Ph.D. Dissertation, 1997, for a comprehensive review and more references.