Gardner W.A. Statistical spectral analysis: a nonprobabilistic theory

Englewood Cliffs: Prentice Hall, 1988. — 592 p.Part I of the book reformulates the entire problem of statistical spectral analysis in terms of time averages instead of the traditional but more abstract ensemble averages.
Part II builds on this theory and methodology by extending and generalizing it from statistically stationary data to cyclostationary data.