%0 Journal Article %A M. A. Krasnosel'skii %A A. V. Sobolev %T Spectral clearance of a focusing operator %J Funkcionalʹnyj analiz i ego priloženiâ %D 1983 %P 73-74 %V 17 %N 1 %I mathdoc %U http://geodesic.mathdoc.fr/item/FAA_1983_17_1_a12/ %G ru %F FAA_1983_17_1_a12