%0 Journal Article %T Meetings of the St.~Petersburg Mathematical Society %J Trudy Matematicheskogo Instituta imeni V.A. Steklova %D 2002 %P 827-832 %V 57 %N 4 %I mathdoc %U http://geodesic.mathdoc.fr/item/RM_2002_57_4_a18/ %G en %F RM_2002_57_4_a18