@article{DE_2000_36_2_a10,
     author = {A. A. Gavrilov and O. M. Penkin},
     title = {An analog of the lemma on the normal derivative for an elliptic equation on a stratified set},
     journal = {Differencialʹnye uravneni\^a},
     pages = {226--232},
     publisher = {mathdoc},
     volume = {36},
     number = {2},
     year = {2000},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_2000_36_2_a10/}
}