%0 Journal Article
%A P. M. Akhmet'ev
%T A higher-order analog of the helicity number for a~pair of divergent-free vector fields
%J Zapiski Nauchnykh Seminarov POMI
%D 2001
%P 15-23
%V 279
%I mathdoc
%U http://geodesic.mathdoc.fr/item/ZNSL_2001_279_a1/
%G ru
%F ZNSL_2001_279_a1