@article{AM2_1975__12_136520,
     author = {H. Schwerdtfeger},
     title = {Invariants of a class of transformation groups. {(Short} {Communication).}},
     journal = {Aequationes mathematicae},
     pages = {318--319},
     publisher = {mathdoc},
     volume = {12},
     year = {1975},
     url = {http://geodesic.mathdoc.fr/item/AM2_1975__12_136520/}
}