[Wikipedia](http://en.wikipedia.org/wiki/Butterfly_diagram) presents butterfly as "a portion of the computation that combines the results of smaller discrete Fourier transforms (DFTs) into a larger DFT, or vice versa (breaking a larger DFT up into subtransforms). The name "butterfly" comes from the shape of the data-flow diagram in the radix-2 case ..."


The question is: What was the first time that FFT was represented by *Butterfly Diagram* ? References would be appreciated.



FFT and Butterfly Diagram
A little idle google scholaring on "fft and butterfly" (restricted to the years 1965-1970) turned up a 1969 Lincoln Laboratory Technical Report (#468), "Quantization Effects in Digital Filters," by C.J. Weinstein, which contains the phrase, 



> 
> This computation, referred to as a
>  'butterfly,'...
> 
> 
> 


beside a figure that does indeed look like a plausible geometric sketch of a butterfly. 


The report is available at <http://www.dtic.mil/cgi-bin/GetTRDoc?AD=AD0706862> . Portions of it, including the "butterfly" figure, reappear in a joint paper with A.V. Oppenheim, "Effects of Finite Register Length in Digital Filtering and the Fast Fourier Transform," published in 1972 in the *Proceedings of the IEEE* (vol. 60, no. 8, pp. 957-976, available at <http://www.rle.mit.edu/dspg/documents/EffectsFFTComplete.pdf> .


