Redshifted 21cm Line Absorption by Intervening Galaxies
  The present generation of radio telescopes, combined with powerful new spectrometers, is opening a new age of redshifted radio absorption-line studies. Outfitting of arrays of antennas, such as the European VLBI Network and the upgraded VLA, with flexibly tuned receivers, will measure sizes and kinematics of intervening galaxies as a function of cosmic time. 
F.H. Briggs