@article{MZM_1971_9_1_a11,
     author = {V. A. Kondrat'ev and S. D. \'Eidel'man},
     title = {Region of positivity of solutions of elliptic equations},
     journal = {Matemati\v{c}eskie zametki},
     pages = {83--87},
     publisher = {mathdoc},
     volume = {9},
     number = {1},
     year = {1971},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MZM_1971_9_1_a11/}
}