@article{SM_1969_8_1_a0,
     author = {M. I. Vishik and V. V. Grushin},
     title = {On~a~class of higher order degenerate elliptic equations},
     journal = {Sbornik. Mathematics},
     pages = {1--32},
     publisher = {mathdoc},
     volume = {8},
     number = {1},
     year = {1969},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/SM_1969_8_1_a0/}
}