@article{10_4064_am_7_3_235_253,
     author = {A. Rybarski},
     title = {Angen\"aherte {Schwingungsfrequenzformeln} f\"ur konservative {Systeme.} {I}},
     journal = {Applicationes Mathematicae},
     pages = {235--253},
     publisher = {mathdoc},
     volume = {7},
     number = {3},
     year = {1963},
     doi = {10.4064/am-7-3-235-253},
     zbl = {0129.16804},
     language = {de},
     url = {http://geodesic.mathdoc.fr/articles/10.4064/am-7-3-235-253/}
}