@article{NUMA_1969__13_131906,
     author = {J.E. OSBORN},
     title = {A {Note} on a {Perturbation} {Theorem} for the {Matrix} {Eigenvalue} {Problem.}},
     journal = {Numerische Mathematik},
     pages = {152--153},
     publisher = {mathdoc},
     volume = {13},
     year = {1969},
     zbl = {0186.05703},
     url = {http://geodesic.mathdoc.fr/item/NUMA_1969__13_131906/}
}