Formula for output autocorrelation and spectrum of a Volterra system with stationary Gaussian input

It is shown how the output autocorrelation and spectrum of a time-invariant Volterra system with stationary Gaussian input can conveniently be found by converting the Volterra series into a Hermite functional series and then making use of the orthogonality property. The paper extends previous work by the author to derive the well-known formula of Bedrosian-Rice.