@article{SM_1971_14_4_a8,
     author = {T. G. Pletneva and S. D. \`Eidel'man and V. A. Kondrat'ev},
     title = {On positive solutions of elliptic equations},
     journal = {Sbornik. Mathematics},
     pages = {587--613},
     publisher = {mathdoc},
     volume = {14},
     number = {4},
     year = {1971},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/SM_1971_14_4_a8/}
}