P waves only

<I>WI>_{<I>PI>,<I>xI>} = <I>W₁₁I> (9)

$$\begin{eqnarray} W_{P,xnmo} = W_{44} + \frac {(W_{13} + W_{44})^2} {W_{33} - W_{44}}\end{eqnarray}$$ (10)

<I>WI>_{<I>PI>,<I>zI>} = <I>W₃₃I> (11)

$$\begin{eqnarray} W_{P,znmo} = W_{44} + \frac {(W_{13} + W_{44})^2} {W_{11} - W_{44}}\end{eqnarray}$$ (12)