Paper: Proper Motions and the Distance to a Water Vapor Maser in the Galaxy M33 Volume: 144, Radio Emission from Galactic and Extragalactic Compact Sources, IAU Colloquium 164 Page: 235 Authors: Argon, A. L.; Greenhill, L. J.; Moran, J. M.; Reid, M. J.; Menten, K. M. Abstract: The relative proper motions of water vapor maser features in the H ii region IC 133 have been used to determine a distance to the galaxy M33 that is independent of the usual calibrations associated with extragalactic distance estimates, \eg, extinction and metallicity.