The independent scattering approximation in the saturated regime
  We show that a saturable single-frequency elastic T-matrix approach to scattering of light by atoms agrees remarkably well with a master equation description in the regime of unsaturated atoms, or for large separation between the atoms. If the atoms are in each other's near-field and the saturation of the atoms is high enough, the two approaches yield different results. 
Tom Savels, Allard P. Mosk and Ad Lagendijk