@article{SM_1968_6_1_a1,
     author = {V. G. Hryptun},
     title = {Function classes quasianalytic relative to first order partial differential operators},
     journal = {Sbornik. Mathematics},
     pages = {17--31},
     year = {1968},
     volume = {6},
     number = {1},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/SM_1968_6_1_a1/}
}