Formula_12558

\[\begin{gathered}\iint f(\boldsymbol{p}, \boldsymbol{r}) d^{3} \boldsymbol{v} d^{3} \boldsymbol{r}=N, \\\boldsymbol{v}=\boldsymbol{p} / m, \quad d^{3} \boldsymbol{v}=d v_{x} d v_{y} d v_{z} .\end{gathered}\]