Before revision: M. Verhaegen, "Subspace Techniques in System Identification", in Encyclopedia of Systems and Control, URL An extension to the stochastic realization problem where we have knowledge only of the Auto-correlation (covariance) function of the output of an LTI system driven by white noise, was derived by researchers like Akaike.H.
After revision: An extension to the stochastic realization problem where we have knowledge only of the Auto-correlation (covariance) function of the output of an LTI system driven by white noise, was derived by researchers like Akaike.H.