The Broad Line Region in Active Galactic Nuclei
  We review constraints on models of the broad line region that are imposed by observations of the emission lines in Active Galactic Nuclei. Comparison of high and low ionization lines in sources with FWHM Hbeta < 4000 km/s points toward low ionization line emission produced in a flattened geometry (the accretion disk?) with an associated high ionization wind. It remains unclear whether these results can be extended to all radio quiet AGN and particularly to radio loud AGN. 
D. Dultzin-Hacyan, P. Marziani, J. W. Sulentic