@article{TRSPY_1979_150_a7,
     author = {G. G. Kazaryan and V. N. Markaryan},
     title = {Hypoellipticity criteria in terms of power and strength of operators},
     journal = {Informatics and Automation},
     pages = {128--142},
     publisher = {mathdoc},
     volume = {150},
     year = {1979},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/TRSPY_1979_150_a7/}
}