Formula_2807

\[\begin{gathered}u(x, t)=v(\boldsymbol{x}, t)+\left(4 \pi c^{2} t\right)^{-1} \int_{S} \rho(y) d S_{y}+ \\+\left(4 \pi c^{2}\right)^{-1}(\partial / \partial t) t^{-1} \int_{S} \varphi(\boldsymbol{y}) d S_{y},\end{gathered}\]