\[u(x,y,t)=c+2\frac{{\partial}^{2}}{{\partial x}^{2}}\ln\left(\theta\left(%
\mathbf{k}x+\mathbf{l}y+\boldsymbol{{\omega}}t+\boldsymbol{{\phi}}\middle|%
\boldsymbol{{\Omega}}\right)\right),\]