The development of fast Fourier transform is attributed to Cooley & Tukey, both have written a lot about it is historical development. However, I am searching early publications which showed how people made the discrete frequency axis after FFT.
For example, if we have N data points (N is an even or odd number), the FFT output also consists of N data points. The specific question is:
(i) Who came up with the equation or the proof that the frequency spacing in discrete Fourier transform is = k/L, where k =0,1,2,3,..., N-1 and L is the total duration of time for which the signal was acquired.
(ii) I am sure the concept of folding or aliasing must be in the same work.
Here is one earlier example by Tukey himself from 1950s