TY  - JOUR
AU  - P. M. Akhmet'ev
TI  - A higher-order analog of the helicity number for a~pair of divergent-free vector fields
JO  - Zapiski Nauchnykh Seminarov POMI
PY  - 2001
SP  - 15
EP  - 23
VL  - 279
PB  - mathdoc
UR  - http://geodesic.mathdoc.fr/item/ZNSL_2001_279_a1/
LA  - ru
ID  - ZNSL_2001_279_a1
ER  -