Voir la notice de l'article provenant de la source Numdam
@article{CM_1992__82_2_137_0, author = {Langmann, Klaus}, title = {Der {4-Werte-Satz} in der {Zahlentheorie}}, journal = {Compositio Mathematica}, pages = {137--142}, publisher = {Kluwer Academic Publishers}, volume = {82}, number = {2}, year = {1992}, mrnumber = {1157937}, zbl = {0784.11010}, language = {de}, url = {http://geodesic.mathdoc.fr/item/CM_1992__82_2_137_0/} }
Langmann, Klaus. Der 4-Werte-Satz in der Zahlentheorie. Compositio Mathematica, Tome 82 (1992) no. 2, pp. 137-142. http://geodesic.mathdoc.fr/item/CM_1992__82_2_137_0/