%0 Journal Article %A B. N. Khimchenko %T On a theorem of M.\,V.~Keldysh and M.\,A.~Lavrent’ev %J Doklady Akademii Nauk %D 1970 %P 46-47 %V 192 %N 1 %I mathdoc %U http://geodesic.mathdoc.fr/item/DAN_1970_192_1_a10/ %G ru %F DAN_1970_192_1_a10