@article{NUMA_1972__19_132140,
     author = {R.S. Varga and J.G. Pierce},
     title = {Higher {Order} {Convergence} {Results} for the {Rayleigh-Ritz} {Method} {Applied} to {Eigenvalue} {Problems:} 2. {Improved} {Error} {Bounds} for {Eigenfunctions.}},
     journal = {Numerische Mathematik},
     pages = {155--169},
     publisher = {mathdoc},
     volume = {19},
     year = {1972},
     zbl = {0223.65080},
     url = {http://geodesic.mathdoc.fr/item/NUMA_1972__19_132140/}
}