\input amstex

$$\int_{t_0}^t\int_{t_0}^tf(\xi)\,\hbox{d}\xi\,\hbox{d}\xi=\Bigl(\xi\cdot\int_{t_0}^tf(\xi)\,\hbox{d}\xi\Bigr)\Big|_{t_0}^t-\int_{t_0}^t\xi\cdot\Bigl(\int_{t_0}^tf(\xi)\,\hbox{d}\xi\Bigr)'_{\xi}\,\hbox{d}\xi$$
\bye