For questions dealing with the Poisson Summation Formula
The Poisson Summation Formula expresses a relation between the Fourier Series Coefficients of a periodic function and the values of its Fourier Transform given by
$$\sum_{n=-\infty}^\infty f(x+n)~=~\sum_{k=-\infty}^\infty e^{2\pi i kx}\int_{-\infty}^\infty f(t)e^{-2\pi ikt}\mathrm dt$$
