Double point self-transverse immersions of

A self-transverse immersion of a smooth manifold M^8k in has a double point self-intersection set which is the image of an immersion of a smooth four-dimensional manifold, cobordent to P⁴, P²×P², P⁴+P²×P² or a boundary. We will prove that for any value of k>1 the double point self-intersection set is a boundary. If k=1, then there exists an immersion of P²×P²×P²×P² in with double point manifold boundary and odd number of triple points. In particular any immersion of oriented manifold in this dimension has double point manifold cobordant to a boundary.