− | N&=\underset{momenta}\int\text{d}^{3}\mathbf{p}\underset{positions}\int\text{d}^{3}\mathbf{r}f(\mathbf{r},\mathbf{p},t) | + | N &=\underset{momenta}\int\text{d}^{3}\mathbf{p}\underset{positions}\int\text{d}^{3}\mathbf{r}f(\mathbf{r},\mathbf{p},t)\\[5pt] |
| &=\underset{momenta}\iiint\; \; \; \underset{positions}\iiint f(x,y,z,p_{x},p_{y},p_{z},t)\; \text{d}x\,\text{d}y\,\text{d}z\,\text{d}p_x\,\text{d}p_y\,\text{d}p_z | | &=\underset{momenta}\iiint\; \; \; \underset{positions}\iiint f(x,y,z,p_{x},p_{y},p_{z},t)\; \text{d}x\,\text{d}y\,\text{d}z\,\text{d}p_x\,\text{d}p_y\,\text{d}p_z |