@article{JRAM_1931__165_149768,
     author = {Ernst Jacobsthal},
     title = {\"Uber das {Schwarzsche} {Lemma.}},
     journal = {Journal f\"ur die reine und angewandte Mathematik},
     pages = {59--63},
     publisher = {mathdoc},
     volume = {165},
     year = {1931},
     zbl = {57.0349.04},
     url = {http://geodesic.mathdoc.fr/item/JRAM_1931__165_149768/}
}