@article{SM_1972_16_3_a7,
     author = {V. G. Maz'ya},
     title = {On a~degenerating problem with directional derivative},
     journal = {Sbornik. Mathematics},
     pages = {429--469},
     publisher = {mathdoc},
     volume = {16},
     number = {3},
     year = {1972},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/SM_1972_16_3_a7/}
}