%0 Journal Article %A V. I. Sumin %T Strong degeneration of singular controls in distributed problems %J Doklady Akademii Nauk %D 1991 %P 295-299 %V 320 %N 2 %I mathdoc %U http://geodesic.mathdoc.fr/item/DAN_1991_320_2_a7/ %G ru %F DAN_1991_320_2_a7