Qualitative aspects of quasar microlensing with two mass components:   magnification patterns and probability distributions
  It has been conjectured that the distribution of magnifications of a point source microlensed by a population of intervening point masses is independent of its mass spectrum. We present gedanken experiments that cast doubt on this conjecture and numerical simulations that show it to be false. 
Paul L. Schechter, Joachim Wambsganss, Geraint F. Lewis