@article{NUMA_1971__18_132090,
     author = {G.W. Stewart},
     title = {On a {Companion} {Operator} for {Analytic} {Functions.}},
     journal = {Numerische Mathematik},
     pages = {26--43},
     publisher = {mathdoc},
     volume = {18},
     year = {1971},
     zbl = {0211.18805},
     url = {http://geodesic.mathdoc.fr/item/NUMA_1971__18_132090/}
}