We study the regularity properties of the Hausdorff distance between spectra
of continuous Harper-like operators. As a special case we obtain H\"{o}lder
continuity of this Hausdorff distance with respect to the intensity of the
magnetic field for a large class of magnetic elliptic (pseudo)differential
operators with long range magnetic fields.Comment: to appear in the Proceedings of the 'Spectral Days' conference,
Santiago de Chile 201
