@article{SM_1970_12_2_a2,
     author = {Ya. A. Roitberg},
     title = {Homeomorphism theorems and {a~Green's} formula for general elliptic boundary problems with nonnormal boundary conditions},
     journal = {Sbornik. Mathematics},
     pages = {177--212},
     publisher = {mathdoc},
     volume = {12},
     number = {2},
     year = {1970},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/SM_1970_12_2_a2/}
}