%0 Journal Article %A Ya. A. Roitberg %A Z. G. Sheftel %T A~theorem on homeomorphisms for elliptic systems and its applications %J Sbornik. Mathematics %D 1969 %P 439-465 %V 7 %N 3 %I mathdoc %U http://geodesic.mathdoc.fr/item/SM_1969_7_3_a9/ %G en %F SM_1969_7_3_a9