Nonlinear Shear-free Radiative Collapse
  We study realistic models of relativistic radiating stars undergoing gravitational collapse which have vanishing Weyl tensor components. Previous investigations are generalised by retaining the inherent nonlinearity at the boundary. We transform the boundary condition to an Abel equation of the first kind. A variety of nonlinear solutions are generated all of which can be written explicitly. Several classes of infinite solutions exist. 
S. S. Misthry, S. D. Maharaj, P. G. L. Leach