\begin{definition}[Definition:Even Impulse Pair Function/2 Dimensional]
Let $\operatorname {II}: \R \to \R$ denote the '''even impulse pair function'''.
The $2$-dimensional form of $\operatorname {II}$ is defined and denoted:
:$\forall x, y \in \R: \map {\operatorname { {}^2 II} } {x, y} := \map {\operatorname {II} } x \map {\operatorname {II} } y$
\end{definition}