Formula_7006

\[\{f, h\}=\sum_{\mathbf{k}=0}^{l}\left(\frac{\partial f}{\partial u_{\mathbf{k}}} \frac{\partial^{\mathbf{k}} h}{\partial x^{\mathbf{k}}}-\frac{\partial h}{\partial u_{\mathbf{k}}} \frac{\partial^{\mathbf{k}} f}{\partial x^{\mathbf{k}}}\right) .\]