@article{MAN_1962__148_161000,
     author = {H.H. JOHNSON},
     title = {Classical {Differential} {Invariants} and {Applications} to {Partial} {Differential} {Equations.}},
     journal = {Mathematische Annalen},
     pages = {308--329},
     publisher = {mathdoc},
     volume = {148},
     year = {1962},
     zbl = {0171.06301},
     url = {http://geodesic.mathdoc.fr/item/MAN_1962__148_161000/}
}