  The Compton amplitude is calculated in terms of expectation values of
light-ray quark operators. As a technical tool we apply the nonlocal light-cone
expansion. Thereby we express the expectation value of the vector light-ray
operator with the help of the expectation value of the corresponding scalar
operator of twist 2. This allows important simplifications. In the limit of
forward scattering the integral relations between the twist-2 contributions of
the structure functions are implied directly.
