@article{ELMA_1956__11_140649,
     author = {H. Wagner},
     title = {Eine {N\"aherungsformel} f\"ur die {Schwingungsdauer} eines {Pendels.}},
     journal = {Elemente der Mathematik},
     pages = {82--86},
     publisher = {mathdoc},
     volume = {11},
     year = {1956},
     zbl = {0070.40908},
     url = {http://geodesic.mathdoc.fr/item/ELMA_1956__11_140649/}
}