On the concave and convex solutions of mixed convection boundary layer   approximation in a porous medium
  In this paper we investigate the similarity solutions of a plane mixed convection boundary layer flow near a semi-vertical plate, with a prescribed power law function of the distance from the leading edge for the temperature, that is embedded in a porous medium. We show the existence and uniqueness of convex and concave solutions for positive values of the power law exponent. 
B. Brighi, J.-D. Hoernel