  In an earlier paper [4], we derived asymptotic formulas for the number of
representations of zero and of large positive integers by the cubic forms in
seven variables which can be written as $L_1(x_1,x_2,x_3) Q_1(x_1,x_2,x_3)+
L_2(x_4,x_5,x_6) Q_2(x_4,x_5,x_6) + a_7 x_7^3$ where $L_1$ and $L_2$ are linear
forms, $Q_1$ and $Q_2$ are quadratic forms and $a_7$ is a non-zero integer and
for which certain quantities related to $L_1Q_1$ and $L_2Q_2$ were non-zero. In
this paper, we consider the case when one or both of these quantities is zero
but $L_1Q_1$ and $L_2Q_2$ are still nondegenerate cubic forms in three
variables.
