  A novel procedure for the nonlinear superposition of two self-similar
solutions of the heat conduction equation with power-law nonlinearity is
introduced. It is shown how the boundary conditions of the superposed state
conflicts with self-similarity, rendering the nonlinearly superposed state to
be a non-exact solution. It is argued that the nonlinearity couples with the
presence of the scale so that the superposition in the linear case can give an
exact solution.
