Comparison of Gaia DR2 Parallaxes of Stars with VLBI Astrometry
  We compare the parallaxes of stars from VLBI astrometry in the literature to
those in the Gaia DR2 catalog. Our full sample contains young stellar objects,
evolved AGB stars, pulsars and other radio stars. Excluding AGB stars, which
show significant discrepancies between Gaia and VLBI parallaxes, and stars in
binary systems, we obtain an average, systematic, parallax offset of $-75 \pm
29~\mu$as for Gaia DR2, consistent with their estimate of a parallax zero-point
between $-100$ and 0 $\mu$as.
