@article{CMH_1934__7_138627,
     author = {Egon Ullrich},
     title = {\"Uber ein {Problem} von {Herrn} {Speiser.}},
     journal = {Commentarii mathematici Helvetici},
     pages = {63--66},
     publisher = {mathdoc},
     volume = {7},
     year = {1934},
     zbl = {0009.40402},
     url = {http://geodesic.mathdoc.fr/item/CMH_1934__7_138627/}
}