@article{MAN_1884__23_157110,
     author = {Engel},
     title = {Zur {Theorie} der {Ber\"uhrangstransformationen.}},
     journal = {Mathematische Annalen},
     pages = {1--44},
     publisher = {mathdoc},
     volume = {23},
     year = {1884},
     url = {http://geodesic.mathdoc.fr/item/MAN_1884__23_157110/}
}