Optical Spectra of Candidate Southern Hemisphere International Celestial
  Reference Frame (ICRF) radio sources
  We present the results of spectroscopic observations of the optical
counterparts of 47 southern radio sources from the candidate International
Celestial Reference Catalogue (ICRC), as part of a Very Long Baseline
Interferometry (VLBI) program to strengthen the celestial reference frame,
especially in the south. The observations were made with the 3.58-meter
European Southern Observatory New Technology Telescope (NTT). We obtained
redshifts for 30 quasars and one radio galaxy, with a further 7 objects being
probable BL Lac objects with featureless spectra. Of the remainder, four were
clear misidentifications with Galactic stars and five had low signal-to-noise
spectra and could not be classified. These results, in combination with new
VLBI data of the radio sources with redshifts more than 2, add significantly to
the existing data needed to refine the distribution of source proper motions
over the celestial sphere.
