@article{GDZPPN002296357,
title = {\"Uber konservative Transformationen.},
journal = {Mathematische Annalen},
volume = {163},
year = {1966},
pages = {44-61},
url = {http://dml.mathdoc.fr/item/GDZPPN002296357}
}
HELMBERG, G. Über konservative Transformationen.. Mathematische Annalen, Tome 163 (1966) pp. 44-61. http://gdmltest.u-ga.fr/item/GDZPPN002296357/