$\forall$$T$:Type, ${\it as}$,${\it bs}$,${\it cs}$:($T$ List).
\\[0ex]iseg($T$; ${\it cs}$; ${\it as}$) $\Rightarrow$ ($\forall$$b$:$T$. (${\it cs}$ = append(${\it as}$; cons($b$; ${\it bs}$))) $\Leftarrow\!\Rightarrow$ False)