Correlation Functions of the XXZ model for $\Delta<-1$
  A new approach to the correlation functions is presented for the XXZ model in the anti-ferroelectric regime. The method is based on the recent realization of the quantum affine symmetry using vertex operators. With the aid of a boson representation for the latter, an integral formula is found for correlation functions of arbitrary local operators. As a special case it reproduces the spontaneous staggered polarization obtained earlier by Baxter. 
Michio Jimbo, Kei Miki, Tetsuji Miwa, Atsushi Nakayashiki