Gravitational Lensing Limits on Early-Type Galaxies
  Gravitational lenses are a unique new constraint on the structure of galaxies. We review the evidence that most lenses are early-type galaxies, the optical properties of the lens galaxies, the evidence against constant M/L models, recent work on the axis ratios of the mass distribution, and the role stellar dynamics plays in gravitational lensing. 
C.S. Kochanek and C.R. Keeton (Harvard-Smithsonian Center for   Astrophysics)