@article{MM_1995_7_5_a36,
     author = {G. A. Smolkin},
     title = {On the hypoellipticity of a~special class of differential operators},
     journal = {Matemati\v{c}eskoe modelirovanie},
     pages = {63},
     publisher = {mathdoc},
     volume = {7},
     number = {5},
     year = {1995},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MM_1995_7_5_a36/}
}