SKRZYŃSKI, M. A note on preserving the spark of a matrix. Annales Universitatis Paedagogicae Cracoviensis Studia Mathematica, [S. l.], v. 14, p. 63–67, 2015. Disponível em: https://studmath.uken.krakow.pl/article/view/13154. Acesso em: 31 oct. 2026.