@article{10_1090_S0894_0347_1995_1311820_X,
     author = {Bryant, Robert L. and Griffiths, Phillip A.},
     title = {Characteristic cohomology of differential systems. {I.} {General} theory},
     journal = {Journal of the American Mathematical Society},
     pages = {507--596},
     publisher = {mathdoc},
     volume = {08},
     number = {3},
     year = {1995},
     doi = {10.1090/S0894-0347-1995-1311820-X},
     url = {http://geodesic.mathdoc.fr/articles/10.1090/S0894-0347-1995-1311820-X/}
}