@article{SM_1969_9_4_a0,
     author = {M. I. Vishik and V. V. Grushin},
     title = {Boundary value problems for elliptic equations degenerate on the boundary of a~domain},
     journal = {Sbornik. Mathematics},
     pages = {423--454},
     publisher = {mathdoc},
     volume = {9},
     number = {4},
     year = {1969},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/SM_1969_9_4_a0/}
}