\vec{B}(\vec{r},t) = \frac{\mu_0}{4\pi}\int{\left(\frac{\vec{J}(\vec{r'},t_r)\times\vec{R}}{R^3}+\frac{1}{R^2c}\frac{\partial \vec{J}(\vec{r'},t_r)}{\partial t}\times\vec{R}\right)\mathrm{d}^3\vec{r'}}