  A complete description of $Q$-conditional symmetries of
reaction-diffusion-convection equation with arbitrary power nonlinearities is
finished. It is shown that the results obtained in the first and second parts
of this work (see arXiv:math-ph/0612078 and arXiv:0706.0814) cannot be extended
on new power nonlinearities arising in the diffusion and convection
coefficients.
