Correlation functions for quantum integrable models

I shall formulate the main problem of the Quantum Field Theory which consists in computing the correlation functions. I shall explain how this problem is tackled for the integrable models putting stress on the application of the Operator Product Expansion (OPE). The OPE are controlled by the methods of the Conformal Field Theory (CFT). Accepting this fact the computation of the correlation functions is reduced to the case of one-point functions. I shall explain that the one-point functions can be computed using the fermionic structure of the integrable models which was found recently.