LaTeX.org

Thanks, Stefan.

Here's a way to use the enumitem package in order to customize your iterated lists and get the "/ref" command to reference your equations properly.

\usepackage{enumitem}
....
\begin{enumerate}[label=(E\arabic*), ref=(E\arabic*)]
\item blah \label{eq1}
\item blah \label{eq2}
\end{enumerate}

Check ...

A simpler solution, using enumerate:

\begin{enumerate}[(E1)]
\item $first$ \label{un}
\item $second$ \label{deux}
\item $third$. \label{trois}
\end{enumerate}

The only issue here is that when you try to reference one of these equations, it'll show a number such as "1" (or "(1)" with \eqref ...