%0 Journal Article %A A. T. Fomenko %T A bordism theory for integrable nondegenerate Hamiltonian systems with two degrees of freedom. A new topological invariant of higher-dimensional integrable systems %J Izvestiya. Mathematics %D 1992 %P 731-759 %V 39 %N 1 %U http://geodesic.mathdoc.fr/item/IM2_1992_39_1_a2/ %G en %F IM2_1992_39_1_a2