And because the spectrum of the discrete time signal, this exact same spectrum will periodically repeat if we extended the frequency higher past $f_s$ these kinds of that the spectrum revealed is likewise the exact same spectrum in every single frequency band from $nf_s$ to $(n+1)f_s$ for any integer $n$. https://www.tumblr.com/pginsector15gurugram/790285487683305472/book-modern-pg-for-boys-in-gurgaon-osmstays?source=share