ns.    --------------------------------------------------------------------------------------------------------------------------------    $A_0$    $A_0$    $B_0$    $B_0$        $\langle       $\langle A_0 B_0 \rangle$   $\langle A_0   $\langle A_0 B_0 \rangle$                                          A_0 B_0 \rangle$                               B_0 \rangle$                                 -------- -------- -------- -------- ------------------ --------------------------- -------------- --------------------------- --     $S+$     $S+$     $S