“…For more details on inertias and ranks of symmetric matrices and relations between inertias and L öwner partial ordering of symmetric matrices, see, e.g., [15,18,19,24]. As further reference for comparison of covariance matrix of predictors/estimators by using matrix rank/inertia method, we may mention [6,22,23] among others. More related work on prediction/estimation problems under partitioned linear models can be found in; see, e.g., [5, 7-12, 14, 17, 25].…”