\begin{tabbing}
$\forall$\=$E$,$X_{1}$,$X_{2}$:Type, ${\it dE}$:EqDecider($E$), ${\it dL}$:EqDecider(IdLnk), ${\it pred?}$:($E$$\rightarrow$(?$E$)),\+
\\[0ex]${\it info}$:($E$$\rightarrow$((:Id $\times$ $X_{1}$) + (:(:IdLnk $\times$ $E$) $\times$ $X_{2}$))),
\\[0ex]$p$:(\=$\forall$$e$:$E$, $l$:IdLnk.\+
\\[0ex]$\exists$\=${\it e'}$:$E$\+
\\[0ex]($\forall$${\it e''}$:$E$. 
\\[0ex]($\uparrow$rcv?(${\it e''}$))
\\[0ex]$\Rightarrow$ (sender(${\it e''}$) = $e$)
\\[0ex]$\Rightarrow$ (link(${\it e''}$) = $l$)
\\[0ex]$\Rightarrow$ (((${\it e''}$ = ${\it e'}$) $\vee$ ${\it e''}$ $<$ ${\it e'}$) $\wedge$ (loc(${\it e'}$) = destination($l$) $\in$ Id)))),
\-\-\\[0ex]$e$:$E$, $l$:IdLnk.
\-\\[0ex]SWellFounded(pred!($e$;${\it e'}$))
\\[0ex]$\Rightarrow$ ($\forall$$e$:$E$. ($\neg$($\uparrow$first($e$))) $\Rightarrow$ (loc(pred($e$)) = loc($e$) $\in$ Id))
\\[0ex]$\Rightarrow$ ($\forall$$e$,${\it e'}$:$E$. (loc($e$) = loc(${\it e'}$) $\in$ Id) $\Rightarrow$ (${\it pred?}$($e$) = ${\it pred?}$(${\it e'}$)) $\Rightarrow$ ($e$ = ${\it e'}$))
\\[0ex]$\Rightarrow$ \=($\forall$$r$:$E$. \+
\\[0ex]($r$ $\in$ receives(${\it dE}$; ${\it dL}$; ${\it pred?}$; ${\it info}$; $p$; $e$; $l$))
\\[0ex]$\Leftarrow\!\Rightarrow$ (($\uparrow$rcv?($r$)) c$\wedge$ ((sender($r$) = $e$) $\wedge$ (link($r$) = $l$))))
\-
\end{tabbing}