The Wess-Zumino-Witten models on N-punctured Riemann sphere

WZW models on the N-punctured Riemann sphere S2 are discussed. The Ward identity is derived. According to Riemann-Roch theorem, we construct a basis of meromorphic λ differentials. The expanding coefficients of the stress-energy tensor and currents are expressed by the meromorphic λ = -1 and λ = 0 differentials. Thus multi-pole Virasoro and Kac-Moody algebra are obtained. A highest-weight representation of the combined multi-pole Kac-Moody and Virasoro algebra are generated. (author). 11 refs