@article{JRAM_1993__445_153576,
     author = {G\"unter Stolz and Joachim Weidmann},
     title = {Approximation of isolated eigenvalues of ordinary differential operators.},
     journal = {Journal f\"ur die reine und angewandte Mathematik},
     pages = {31--44},
     publisher = {mathdoc},
     volume = {445},
     year = {1993},
     zbl = {0781.34052},
     url = {http://geodesic.mathdoc.fr/item/JRAM_1993__445_153576/}
}