Boundary properties of generalized Cauchy type integrals in the space of smooth functions

The generalized Cauchy type integrals which kernel depends on the difference of arguments are considered on the smooth contour. These integrals cover as potentials of double layer for second order elliptic equations as generalized Cauchy type integrals for first order elliptic systems on the plane. In the paper the sufficient conditions such that these integrals belong $C^{n,\mu}$ up to the boundary are found.