@article{MAN_1966__165_161420,
     author = {G. HELMBERG},
     title = {\"Uber konservative {Transformationen.}},
     journal = {Mathematische Annalen},
     pages = {44--61},
     publisher = {mathdoc},
     volume = {165},
     year = {1966},
     url = {http://geodesic.mathdoc.fr/item/MAN_1966__165_161420/}
}