@article{MZ_1992__210_1_174416,
     author = {Ralph Berr},
     title = {Sums of mixed powers in fields and orderings of prescribed level.},
     journal = {Mathematische Zeitschrift},
     pages = {513--528},
     year = {1992},
     volume = {210},
     number = {1},
     zbl = {0764.12003},
     url = {http://geodesic.mathdoc.fr/item/MZ_1992__210_1_174416/}
}