Form factors, correlation functions and vertex operators in the eight-vertex model at reflectionless points

The eight-vertex model at the reflectionless points is considered on the basis of Smirnov's axiomatic approach. Integral formulae for form factors of the eight-vertex model can be obtained in terms of those of the eight-vertex SOS model, by using vertex-face transformation. The resulting formulae have very simple forms at the reflectionless points, and suggests us the explicit expressions of the type II vertex operators of the eight-vertex model.