“…The bounds permit derivation of asymptotic moments and asymptotic normality for the model estimators. In connection with the estimation of higher-order spectral densities, we should point out that a non-parametric approach has been mainly followed, resulting in periodograms of higher orders and their modifications with the use of smoothing, tapering, shift-in-time methods (see, for example, [19,1,8]). Estimation of parametric models using higher-order information has been developed in the time domain for some particular cases such as AR and ARMA models based on a generalization of the Yule-Walker method (see, for example, [48]).…”