Direction-Preserving and Schur-Monotonic Semi-Separable Approximations of Symmetric Positive Definite Matrices}, article, March 16, 2010; (https://digital.library.unt.edu/ark:/67531/metadc837383/m1/1/: accessed April 19, 2024), University of North Texas Libraries, UNT Digital Library, digital.library.unt.edu; .