A two-component model for ${\gamma }^{\ast }$-p scattering at small Bjorken x

We extend the Golec-Biernat-W"usthoff model for virtual photon - proton scattering to include the resolved photon component explicitly. The parameters of the resolved photon component are taken from the literature, while the parameters of the dipole-nucleon interaction are fitted to the HERA data in a selected limited range of $x$ and $Q^2$. A good agreement with experimental data is obtained far beyond the region of the fit.