Abstract:
An almost Hermitian manifold satisfies the cosymplectic $t$-hypersurfaces axiom, if a cosymplectic hypersurface with type number $t$ passes through every its point. It is proved that if an arbitrary $W_4$-manifold satisfies the cosymplectic $t$-hypersurfaces axiom with $t\leq1$, then this manifold is Kählerian.