I have difficulty in finding references for the following Lemma (284), that I found in a useful lecture of Prof. Cosma Shalizi.
Can anybody provide me some references?
Thank you in advance.
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(Orthogonal Spectral Increments and Weak Stationarity)
The spectral process of a second order process has orthogonal increments if and only if the process is weakly stationary.
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With spectral process it is meant the spectral respresentation of a stochastic process.
http://www.stat.cmu.edu/~cshalizi/754/notes/lecture-22.pdf