@article{JRAM_1839__19_147063,
     author = {Theodor Sch\"onemann},
     title = {Ueber die {Congruenz} x2 + y2 ... 1 (mod.p). {(Theorie} der trignometrischen {Functionen} in {Bezug} auf {Congruenzen).}},
     journal = {Journal f\"ur die reine und angewandte Mathematik},
     pages = {93--112},
     publisher = {mathdoc},
     volume = {19},
     year = {1839},
     url = {http://geodesic.mathdoc.fr/item/JRAM_1839__19_147063/}
}