New conditional symmetries and exact solutions of nonlinear   reaction-diffusion-convection equations. I
  A complete description of Q-conditional symmetries for two classes of reaction-diffusion-convection equations with power diffusivities is derived. It is shown that all the known results for reaction-diffusion equations with power diffusivities follow as particular cases from those obtained here but not vise versa. 
Roman Cherniha and Olexii Pliukhin