\begin{tabbing}
$\forall$${\it es}$:ES, $L$:(Id List).
\\[0ex]fischer($L$)
\\[0ex]$\Rightarrow$ \=($\forall$$e$:E.\+
\\[0ex](loc($e$) $\in$ $L$) $\Rightarrow$ ($\uparrow$"x" changed before $e$) $\Rightarrow$ fEvent((last change to "x" before $e$)))
\-
\end{tabbing}