@article{NUMA_1975__24_132342,
     author = {S. Pruess},
     title = {High {Order} {Approximations} to {Sturm-Liouville} {Eigenvalues.}},
     journal = {Numerische Mathematik},
     pages = {241--248},
     publisher = {mathdoc},
     volume = {24},
     year = {1975},
     zbl = {0298.65058},
     url = {http://geodesic.mathdoc.fr/item/NUMA_1975__24_132342/}
}