[1] A. Albert: Conditions for positive and nonnegative definiteness in terms of pseudo inverse. SIAM. J. Appl. Math. 17 (1969) 434-440. DOI 10.1137/0117041 | MR 0245582

[2] R. Bellmann: Introduction to Matrix Analysis. McGraw Hill, New York (1960). MR 0122820

[3] D. Carlson E. Haynsworth, Th. Markham: Generalization of Schur complement by means of Moore Penrose inverse. SIAM. J. Appl. Math. 26 (1974) 169-175. DOI 10.1137/0126013 | MR 0347843

[4] R. J. Duffin, T. D. Morley: Almost definite operators and electromechanical systems. SIAM. J. Appl. Math. 35 (1978) 21-30. DOI 10.1137/0135003 | MR 0496067

[5] Hans J. Werner: On the Matrix Monotonicity of generalized inversion. J. Linear Algebra and Appl. 27 (1979) 141-145. DOI 10.1016/0024-3795(79)90036-3 | MR 0545727

[6] R. E. Hartwig: A note on the partial orderings on positive semi definite matrices. J. Linear and Multilinear Alg. 6 (1978) 223-226. DOI 10.1080/03081087808817240 | MR 0506330

[7] T. O. Lewis, T. G. Newman: Pseudoinverses of positive semidefinite matrices. SIAM. J. Appl. Math. 10 (1968) 701-703. DOI 10.1137/0116057 | MR 0233826 | Zbl 0164.03102

[8] A R. Meenakshi: On Almost Positive definite matrices. Tech. Report # 8616, Indian Statistical Institute, New Delhi, August 1986.

[9] S. K. Mitra, M. L. Puri: The Fundamental Bordered Matrix of Linear Estimation and the Duffin-Morley General Linear Electromechanical Systems. Applicable Analysis, 14 (1983) 241-258. MR 0701575 | Zbl 0506.15001

[10] S. K. Mitra, P. L. Odell: On parallel Summability of matrices. J. Linear Algebra. Appl. 74 (1986) 239-255. DOI 10.1016/0024-3795(86)90126-6 | MR 0822150 | Zbl 0589.15004