Proper Motions of Dwarf Spheroidal Galaxies from Hubble Space Telescope   Imaging. III: Measurement for Ursa Minor
  This article presents a measurement of the proper motion of the Ursa Minor dwarf spheroidal galaxy determined from images taken with the Hubble Space Telescope in two distinct fields. 
S. Piatek, C. Pryor, P. Bristow, E. Olszewski, H. Harris, M. Mateo, D.   Minniti, C. Tinney