Fiedler, M; Ptak, V. (1962), "On matrices with non-positive off-diagonal elements and positive principal minors", Czechoslovak Mathematical Journal, 12 (3): 382–400, doi:10.21136/CMJ.1962.100526.
Plemmons, R.J. (1977), "M-Matrix Characterizations. I -- Nonsingular M-Matrices", Linear Algebra and its Applications, 18 (2): 175–188, doi:10.1016/0024-3795(77)90073-8.