@article{MZ_1930__32_168224,
     author = {H., Hopf},
     title = {\"Uber die {Verteilung} quadratischer {Reste}},
     journal = {Mathematische Zeitschrift},
     pages = {222--231},
     publisher = {mathdoc},
     volume = {32},
     year = {1930},
     zbl = {56.0157.06},
     url = {http://geodesic.mathdoc.fr/item/MZ_1930__32_168224/}
}