Abstract
In this thesis, we give a new proof of non-neutrality of the Steifel manifolds Vn,k. W.H.Lin proves in [1] this conjecture by a construction on Vn,k and by using the method of second cohomology operations. In this thesis, we give a new proof of this result also by this construction together with Hopf construction, but using only the primary operations (by which we mean Steenord operations).