%0 Journal Article %A M. S. Nikol'skii %T Singular Sets of Extremal Controls in Optimal Control Problems %J Informatics and Automation %D 2019 %P 252-256 %V 304 %I mathdoc %U http://geodesic.mathdoc.fr/item/TRSPY_2019_304_a15/ %G ru %F TRSPY_2019_304_a15