@article{SM_1990_67_1_a16,
     author = {V. A. Kozlov},
     title = {The~strong zero theorem for an~elliptic boundary value problem in an~angle},
     journal = {Sbornik. Mathematics},
     pages = {283--302},
     publisher = {mathdoc},
     volume = {67},
     number = {1},
     year = {1990},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/SM_1990_67_1_a16/}
}