@article{ELMA_1979__34_141236,
     author = {O. Bottema},
     title = {Eine {Erweiterung} der {Stewartschen} {Formel.}},
     journal = {Elemente der Mathematik},
     pages = {138--140},
     publisher = {mathdoc},
     volume = {34},
     year = {1979},
     zbl = {0425.51010},
     url = {http://geodesic.mathdoc.fr/item/ELMA_1979__34_141236/}
}