• [1]

    S. Coleman, Nucl. Phys., B310(1988), 643,[2] T. Banks, Nuc1. Phys., B309(1988), 493,[3] S. Weinberg, Rev. Mod. Phys., 61(1989), 1,[4] S. L, Adler, Phys. Rev. Lett., 62(1989), 373.[5] J. Polchinski, Phys. Lett., B219(1989), 251.[6] J. M. Alberty, Phys, Lett., B221(1989), 250.[7] S. B. Giddings and人.Strominger, Nuc1. Phys., B321(1989), 481.[8] I.Kleranov, L. Susskind and T. Banks, Nucl. Phys., B317(1989), 665.[9] A. Lyons, Nucl. Phyr., 8333(1990), 279.[10] S. B. Giddings and A. Srrominger, Nuc1. Phys., B306(1988), 890.[11] G. V. Lavrelashrili, V. A. Rabakov and P. G. Tinyakov, Mod. Phys. lett., A13(1988), 1231.[12] R. C. Myers., Phys. Rev., D38(1988), 1327; Nucl. Phys., B323(1989), 225.[13] A. K. Gupta, J. Hughes, J. Preskill and M. B. Wise., Nucl. Phys., B333(1990), 195.