@article{MAN_1939__116_160002,
     author = {A.D. MichaI and D.H. Hyers},
     title = {Differential {Invariants} in a {General} {Differential} {Geometry}},
     journal = {Mathematische Annalen},
     pages = {310--333},
     publisher = {mathdoc},
     volume = {116},
     year = {1939},
     zbl = {0020.36905},
     url = {http://geodesic.mathdoc.fr/item/MAN_1939__116_160002/}
}