Let $\emptyset$ be the D13: Empty set.
Let $X_j$ be a D11: Set for each $j \in J$ such that
Let $X_j$ be a D11: Set for each $j \in J$ such that
| (i) | \begin{equation} \exists \, j \in J : X_j = \emptyset \end{equation} |
Then
\begin{equation}
\prod_{j \in J} X_j
= \emptyset
\end{equation}