$\forall$$T$:Type, $L$,$L_{1}$,$L_{2}$:($T$ List).
\\[0ex](($\neg$($\uparrow$null($L$))) $\Rightarrow$ ($\neg$(last($L$) $\in$ $L_{2}$))) $\Rightarrow$ sublist($T$; $L$; append($L_{1}$; $L_{2}$)) $\Rightarrow$ sublist($T$; $L$; $L_{1}$)