\begin{definition}[Definition:Maximizers of Real Function]
Let $f: X \to \R$ be a real-valued function.
The '''set of maximisers''' of a $f$ are denoted:
:$\ds \arg \max_{x \mathop \in X} \map f x$
{{definition wanted|The notation is defined in my source work, but not the concept.}}
\end{definition}