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$s$ SubGrp of $g$
\\[0ex]$\,\equiv$$_{\mbox{\scriptsize def}}$$\;\;$\=$s$(e$g$)\+
\\[0ex]\& ($\forall$$a$:$\mid$$g$$\mid$. ($s$($a$)) $\Rightarrow$ ($s$(($\sim$$g$)($a$))))
\\[0ex]\& ($\forall$$a$:$\mid$$g$$\mid$, $b$:$\mid$$g$$\mid$. ($s$($a$)) $\Rightarrow$ ($s$($b$)) $\Rightarrow$ ($s$($a$ ($\ast$$g$) $b$)))
\-
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