@article{MAN_1897__49_157863,
     author = {E. Gubler},
     title = {Beweis einer {Formel} des {Herrn} {Sonin}},
     journal = {Mathematische Annalen},
     pages = {583--584},
     publisher = {mathdoc},
     volume = {49},
     year = {1897},
     zbl = {28.0411.01},
     url = {http://geodesic.mathdoc.fr/item/MAN_1897__49_157863/}
}