@article{MMO_1969_20_a7,
     author = {L. R. Volevi\v{c} and V. M. Kagan},
     title = {Pseudodifferential hypoelliptic operators in the theory of function spaces},
     journal = {Trudy Moskovskogo matemati\v{c}eskogo ob\^{s}estva},
     pages = {241--275},
     publisher = {mathdoc},
     volume = {20},
     year = {1969},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MMO_1969_20_a7/}
}