@article{SM_1967_2_1_a7,
     author = {B. R. Vainberg and V. V. Grushin},
     title = {Uniformly nonelliptic problems. {II}},
     journal = {Sbornik. Mathematics},
     pages = {111--133},
     publisher = {mathdoc},
     volume = {2},
     number = {1},
     year = {1967},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/SM_1967_2_1_a7/}
}