@article{NUMA_1972__19_132145,
     author = {P. Lancaster},
     title = {A {Note} on {Sub-Multiplicative} {Norms.}},
     journal = {Numerische Mathematik},
     pages = {206--208},
     publisher = {mathdoc},
     volume = {19},
     year = {1972},
     zbl = {0227.15007},
     url = {http://geodesic.mathdoc.fr/item/NUMA_1972__19_132145/}
}