Аннотация:
It is proved that $2$-hypersurfaces and $3$-hypersurfaces of $W_4$-manifolds admit identical almost contact metric structures.
Ключевые слова и фразы:almost contact metric structure, structure of cosymplectic type, almost Hermitian manifold, $W_4$-manifold, locally conformal Kählerian manifold, type number.