$\forall$$T$:Type, $x_{1}$,$x_{2}$:$T$, $L_{1}$,$L_{2}$:($T$ List).
\\[0ex]sublist($T$; cons($x_{1}$; $L_{1}$); cons($x_{2}$; $L_{2}$))
\\[0ex]$\Leftarrow\!\Rightarrow$ ((($x_{1}$ = $x_{2}$) $\wedge$ sublist($T$; $L_{1}$; $L_{2}$)) $\vee$ sublist($T$; cons($x_{1}$; $L_{1}$); $L_{2}$))