Ponzoni, Ignacio, Mabel Sánchez, y Nélida Brignole. 1998. Permutation of Sparse Matrices to a Specific Lower BTF Using Graph Decompositions. Electronic Journal of SADIO (EJS) 1 (1), 76-87. https://publicaciones.sadio.org.ar/index.php/EJS/article/view/136.