%0 Journal Article %A B. N. Ivanov %T Enclosure structures of equal level line fields in the gradient filling problem %J Numerical methods and programming %D 2006 %P 30-40 %V 7 %N 2 %I mathdoc %U http://geodesic.mathdoc.fr/item/VMP_2006_7_2_a7/ %G ru %F VMP_2006_7_2_a7