%0 Journal Article %A V. I. Blagodatskikh %T Letter to the editors: “A sufficient optimality condition” (Differencial'nye Uravnenija 9 (1973), 416–422) %J Differencialʹnye uravneniâ %D 1973 %P 2112 %V 9 %N 11 %U http://geodesic.mathdoc.fr/item/DE_1973_9_11_a28/ %G ru %F DE_1973_9_11_a28