The Broad Emission Line Regions of Quasars - current status and future   prospects
  The spectrum emitted by the Broad Emission Line Regions of Active Galactic Nuclei can measure the luminosity of the central object and the chemical composition of the interstellar medium in a very young galaxy, and so constrain the expansion of the universe and the first stages of the evolution of massive galaxies. Here I review some recent developments in our understanding of the nature of the clouds and the interpretation of their spectra. 
Gary Ferland