Corollary 4

If $\theta_1 \in \mathrm{Ext}_A^n(P, Q)$ is the class associated with the exact sequence $(\mathscr{S}_1)$, we have $\partial^m(\mathscr{S}_1, M)(\alpha) = \theta_1 \circ \alpha$ for all $\alpha \in \mathrm{Tor}_m^A(P, M)$.