## Does anyone know a good derivation of the fact that the spherical harmonic \$Y^m_l\$ is a polynomial of \$l\$th degree in \$x\$, \$y\$ and \$z\$?

Does anyone know a good derivation of the fact that the spherical harmonic $$Y^m_l$$ is a polynomial of $$l$$th degree in $$x$$, $$y$$ and $$z$$?