Galba, E. F., V. S. Deineka, and I. V. Sergienko. 2015. “Necessary and Sufficient Conditions for the Existence of Weighted Singular-Valued Decompositions of Matrices With Singular Weights”. Ukrains’kyi Matematychnyi Zhurnal 67 (3), 406–426. http://umj.imath.kiev.ua/index.php/umj/article/view/1992.