@article{ZNSL_2001_279_a3,
     author = {S. V. Duzhin},
     title = {Infinitesimal classification of systems of two {PDE} of first order},
     journal = {Zapiski Nauchnykh Seminarov POMI},
     pages = {61--69},
     publisher = {mathdoc},
     volume = {279},
     year = {2001},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/ZNSL_2001_279_a3/}
}