@article{IM2_2006_70_2_a4,
     author = {R. A. Sarkisyan},
     title = {On differential invariants of geometric structures},
     journal = {Izvestiya. Mathematics },
     pages = {307--362},
     publisher = {mathdoc},
     volume = {70},
     number = {2},
     year = {2006},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/IM2_2006_70_2_a4/}
}