@article{DAN_1971_201_5_a12,
     author = {Ya. A. Roitberg and Z. G. Sheftel},
     title = {Green{\textquoteright}s formula and homeomorphism theorems for nonlocal elliptic boundary value problems},
     journal = {Doklady Akademii Nauk},
     pages = {1059--1062},
     publisher = {mathdoc},
     volume = {201},
     number = {5},
     year = {1971},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1971_201_5_a12/}
}