[1] T. O. Lewis P. L. Odell: A generalization of the Gauss-Markov theorem. Amer. Stat. Ass. Journal (Dec. 1966), 1063-1066. MR 0203873

[2] P. Kovanic: Minimum penalty estimate. Kybernetika 8 (1972), 5, 367-383. MR 0326947 | Zbl 0246.62073

[3] P. Kovanic: Generalized linear estimate of functions of random matrix arguments. Kybernetika 10 (1974), 4. 303-316. MR 0373722 | Zbl 0284.62038

[4] G. Zysking: On canonical forms, non-negative covariance matiices and best and simple least squares linear estimators in linear models. Ann. Math. Stat. 38 (1966), 1092-1108. MR 0214237

[5] C. R. Hallum T. O. Lewis T. L. Boullion: Estimation in the general linear model with a positive semidefinite covariance matrix. Communications in statistics 1 (2), (1973) 157-166. MR 0317469

[6] R. M. Pringle A. A. Rayner: Generalized inverse matrices with applications to statistics. Griffin, London 1971. MR 0314860