\[x^{2}{M}^{2}\left(x\right)={N'}^{2}\left(x\right)+{N}^{2}\left(x\right){\phi'}%
^{2}\left(x\right)={N'}^{2}\left(x\right)+\pi^{-2}x^{2}{N}^{-2}\left(x\right),\]