Abstract:
In this paper there is proved a generalization of the results of Whitehead and Pontryagin on the homotopy classification of closed, simply connected four-manifolds. Let $W$ and $M$ be compact four-dimensional simply connected oriented four-manifolds. By $q_w$ is denoted the intersection index on the group H2(W).Basic Result. THEOREM (Extension). Let the groups $H_1(\partial W)$ and $H_1(\partial M)$ be finite and suppose given a homotopy equivalence $f:\partial W\to\partial M$. In order that $f$ can be extended to a homotopy equivalence $(W,\partial W)\to(M,\partial M)$, it is necessary and sufficient that there should exist an isomorphism $\Xi$, such that the diagram
$$
\begin{array}{ccc}
H_2(W,\partial W) &
\overset {\partial}\longrightarrow & H_1(\partial W) \\
\downarrow\Xi & &
\downarrow f*\\
H_2(M,\partial M) &
\overset {\partial}\longrightarrow & H_1(\partial W)
\end{array}
$$
is commutative and $\Xi^*q_m=q_w$.