Formula_20718

\[\begin{gathered}J_{\mu}=\{-J / c, \rho\}=q \int_{-\infty}^{\infty} u_{\mu}(\tau) \delta(x-x(\tau)) \delta(y-y(\tau)) \times \\\times \delta(z-z(\tau)) \delta(t-t(\tau)) d \tau,\end{gathered}\]