Formula_2810

\[\begin{gathered}u(x, t)=-\int_{\Omega}(4 \pi r)^{-1} f(\boldsymbol{y}, t-r / c) d \Omega_{y}+ \\+\int_{\sigma}\left[r^{-1} \partial u / \partial n-u \partial r^{-1} / \partial n+(r c)^{-1}(\partial u / \partial \tau) \partial r / \partial n\right] d \sigma / 4 \pi, \\\tau=t-r / c\end{gathered}\]