Formula_3673

\[\begin{gathered}v=\left(f-\sum x_{i} \partial f / \partial x_{i}\right) \partial / \partial z+ \\+\sum\left(\partial f / \partial y_{i}+x_{i} \partial f / \partial z\right) \partial / \partial x_{i}-\sum \partial f / \partial x_{i} \partial / \partial y_{i}\end{gathered}\]