• [1]

    A. M. Polyakov, Mod. Phys, Lett., A2(1987), 893;V. G. Knizhnik, A. M. Polyakov and A. B. Zamolodchikov, Mod. Phys. Lett., A3(1988), 819,[2] J.-L. Gervais, preprint LPTENS 89/14;F. Smirnov and L. Takhtajan, preprint PAMUC 90/12.[3] O. Babelon and C. M. Viallet, preprint SISSA-89-54;E. Cremmer and J.-L. Gervais, Commun. Math. Phys. 134(1990), 619.[4] V. G. Drinfeld, proc. ICM-86, Berkeley, 1(1986), 798;M. Jimbo, Lett. Math. Phys., 10(1985), 63.[5] D. Friedan and S. Shenker, Nucl. Phys,, B281(1987), 509;T. Eguchi and H. Ooguri, Nucl. Phys., B282(1987), 308.[6] D. Gross and A. Migdal, Nucl. Phys., B340(1990), 333.[7] P. G. Zograf and L. A. Takhtajan, Math. USSR Sborrsik, 132(1987), 147.[8] A. F. Beardon,《离散群几何》(中译本)北京理工大学出版社(1988),[9] L. D. Faddeev and L. A. Takhtajan, Lect: Notes in Phys., 246(1986), 166;A. K. Pogrebkov and M. K. Polivanov, Soviet Sci. Rev., C3(1985), 198.[10] L. D. Faddeev, Commun. Math. Phys., 132(1990), 139.[11] N. S. Hawley and M. Schiffer, ,Acta Math，115(1966), 199.