$S_4$ 的子群
$S_4$ 是四个元素的对称群, 其阶为 $|S_4|=4!=24$,
subgroups of S_4 (planetmath.org)
abstract algebra - $D_8$ as a derived subgroup - Mathematics Stack Exchange
$S_4$ 是四个元素的对称群, 其阶为 $|S_4|=4!=24$,
subgroups of S_4 (planetmath.org)
abstract algebra - $D_8$ as a derived subgroup - Mathematics Stack Exchange