same\_order($x_{1}$;$y_{1}$;$x_{2}$;$y_{2}$;$L$;$T$) $\,\equiv$$_{\mbox{\scriptsize def}}$$\;\;$$x_{1}$ $<<$ $y_{1}$ $\in$ $L$ $\Rightarrow$ ($x_{2}$ $\in$ $L$) $\Rightarrow$ ($y_{2}$ $\in$ $L$) $\Rightarrow$ $x_{2}$ $<<$ $y_{2}$ $\in$ $L$