Formula_15656

\[B_{j l}(\boldsymbol{r}, t)=\int_{\mathbb{R}^{3}} e^{i \boldsymbol{k} \boldsymbol{r}} \frac{E(k)}{4 \pi k^{2}}\left(\delta_{j l}-\frac{k_{j} k_{l}}{k^{2}}\right) d \boldsymbol{k}, \quad k=|\boldsymbol{k}|,\]