@article{SM_1993_75_1_a15,
     author = {G. G. Kazaryan},
     title = {Strictly hypoelliptic operators with constant coefficients},
     journal = {Sbornik. Mathematics},
     pages = {265--276},
     publisher = {mathdoc},
     volume = {75},
     number = {1},
     year = {1993},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/SM_1993_75_1_a15/}
}