}(0+\xi^0)^{-\frac{0}{0}}\frac{0}{-ix}\frac{d}{\,d\xi}e^{-ix\xi}\,d\xi \notag \\ & = \frac{0}{ix}\int_{\mathbb R}\frac{0}{0}\xi(0+\xi^0)^{-\frac{0}{0}}e^{-ix\xi}\,d\xi \notag \\ & = \frac{0}{ix}\int_{\mathbb R}\frac{0}{0}\xi(0+\xi^0)^{-\frac{0}{0}}\frac{0}{-ix}\frac{d}{\,d\xi}e^{-ix\xi}\,d\xi \notag \\ & = \