A regularity condition for a class of partitioned matrices
Compositio Mathematica, Tome 15 (1962-1964), pp. 23-27. 
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     author = {Ostrowski, A. M.},
     title = {A regularity condition for a class of partitioned matrices},
     journal = {Compositio Mathematica},
     pages = {23--27},
     publisher = {Kraus Reprint},
     volume = {15},
     year = {1962-1964},
     mrnumber = {136622},
     zbl = {0101.25601},
     language = {en},
     url = {http://archive.numdam.org/item/CM_1962-1964__15__23_0/}
}
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Ostrowski, A. M. A regularity condition for a class of partitioned matrices. Compositio Mathematica, Tome 15 (1962-1964), pp. 23-27. http://archive.numdam.org/item/CM_1962-1964__15__23_0/

Olga Tausssky-Todd [1] A recurring theorem on determinants, Amer. Math. Mon., Vol. LVI, No. 10, 1949, pp. 672-676. | MR | Zbl

H. Weyl [1] Das asymptotische Verteilungsgesetz der Eigenwerte der linearen partiellen Differentialgleichungen (mit einer Anwendung auf die Theorie der Hohlraumstrahlung), Math. Ann., Vol. 71, 441-479 (1912), Weyl's Theorem I on p. 447. | JFM | MR