\begin{tabbing}
$\forall$\=$A$, $B$:Type, $L_{2}$:((${\it tg}$:Id $\times$ ($A$$\rightarrow$$B$$\rightarrow$(Top List))) List), $L$:((:Top $\times$ (:Id $\times$ Top)) List), ${\it tg}$:Id,\+
\\[0ex]$a$:$A$, $b$:$B$.
\-\\[0ex]\{(\=map($\lambda$$x$.$x$.2;$L$)\+
\\[0ex]=
\\[0ex]concat(map($\lambda$${\it tgf}$.map($\lambda$$x$.$<$${\it tgf}$.1, $x$$>$;(${\it tgf}$.2)($a$,$b$));$L_{2}$))
\\[0ex]$\in$ ((${\it tg}$:Id $\times$ Top) List))
\-\\[0ex]$\Rightarrow$ ($\neg$(${\it tg}$ $\in$ map($\lambda$$p$.$p$.1;$L_{2}$)))
\\[0ex]$\Rightarrow$ (filter($\lambda$${\it ms}$.(${\it ms}$.2).1 = ${\it tg}$;$L$) = [] $\in$ ((:Top $\times$ (:Id $\times$ Top)) List))\}
\end{tabbing}