@article{NUMA_1977__29_132511,
     author = {W.G. Kolata},
     title = {Approximation in {Variationally} {Posed} {Eigenvalue} {Problems.}},
     journal = {Numerische Mathematik},
     pages = {159--172},
     publisher = {mathdoc},
     volume = {29},
     year = {1977},
     zbl = {0352.65059},
     url = {http://geodesic.mathdoc.fr/item/NUMA_1977__29_132511/}
}