@article{MZ_1952__57_169326,
     author = {Evan T. Davies},
     title = {On the {Invariant} {Theory} of {Contact} {Transformations.}},
     journal = {Mathematische Zeitschrift},
     pages = {415--427},
     year = {1952},
     volume = {57},
     zbl = {0050.16304},
     url = {http://geodesic.mathdoc.fr/item/MZ_1952__57_169326/}
}