@article{GDZPPN00116953X, title = {A Useful Generalization of the P0 Matrix Concept,.}, journal = {Numerische Mathematik}, volume = {18}, year = {1971}, pages = {62-70}, url = {http://dml.mathdoc.fr/item/GDZPPN00116953X} }
WILLSON, A.N. jr. A Useful Generalization of the P0 Matrix Concept,.. Numerische Mathematik, Tome 18 (1971) pp. 62-70. http://gdmltest.u-ga.fr/item/GDZPPN00116953X/