@article{JRAM_1869__70_148073,
     author = {E.B. Christoffel},
     title = {Ueber die {Transformation} der homogenen {Differentialausdr\"ucke} zweiten {Grades.}},
     journal = {Journal f\"ur die reine und angewandte Mathematik},
     pages = {46--70},
     publisher = {mathdoc},
     volume = {70},
     year = {1869},
     language = {de},
     url = {http://geodesic.mathdoc.fr/item/JRAM_1869__70_148073/}
}