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