Formula_7058

\[\begin{gathered}D\left(x_{1}, x_{2} ; x_{1}^{\prime}, x_{2}^{\prime}\right)=\bar{D}\left(x_{1}, x_{2} ; x_{1}^{\prime}, x_{2}^{\prime}\right)+ \\+\int K\left(x_{1}, x_{2} ; x_{3}, x_{4}\right) D\left(x_{3}, x_{4} ; x_{1}^{\prime}, x_{2}^{\prime}\right) d^{4} x_{3} d^{4} x_{4}\end{gathered}\]