# Reference for Wiener's formula in the context of Fourier

Could anyone point me to an easily available reference for Wiener's formula used in the following answer ?

I tried the most obvious sources without success.

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Isn't this just the Plancherel formula for measures? Perhaps you'll find the Tauberian theorem(s) relevant. –  Steve Huntsman Dec 2 '10 at 15:22

It is a formula usually attributed to Parseval: http://en.wikipedia.org/wiki/Parsevals_theorem

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