solving pressure equation in terms of square pressure
 

Hi there,
I would like to implement a pressure equation which is in terms of square pressure in my code(I'm using OpenFoam) but I got trouble. I tried this
fvm:laplacian(K,pow(p,2))== source term where K is a constant with the right unit
but it seems there is a error message,
do I have to include a specific header? what is it?#include"???"
please can somebody out there help me?