Is $H$ is a subgroup of $D_4?$ Yes/No
35660
Elements of order 2 in $D_{2n}$
99694
Number of subgroups of $S_4$
147298
How to find all subgroups of a direct product?
61379
Let $G$ be abelian, $H$ and $K$ subgroups of orders $n$, $m$. Then G has subgroup of order $\operatorname{lcm}(n,m)$.
22444
Normal subgroups of dihedral groups
98739
If $H$ is a subgroup of $G$ and $K$ is a subgroup of $H$, then $$|G:K|=|G:H||H:K|$$
151862
Is any subgroup of a direct product isomorphic to a direct product of subgroups?
53409
Show group of order $4n + 2$ has a subgroup of index 2.
132342
Suppose $H$ is a subgroup of $S_n$ but $H$ is not a subgroup of $A_n$. Prove that |$H$ ∩ $A_n$| = $\frac{1}{2}|H|$?
132856
Find the derived subgroup of $A_4$
154398
Show that H is a subgroup of G
4883
Let $H$ be a subgroup of a group $G$ such that $x^2 \in H$ , $\forall x\in G$ . Prove that $H$ is a normal subgroup of $G$
14895
Reference for the subgroup structure of $\rm{PSL}_2(q)$
125498
Check whether subgroup is normal in $ S_4$
100974
Showing H is a normal subgroup by calculating left and right coset
150042
Prove $x^{-1}Hx$ is a subgroup of $G$
151727
If $|G/H|=4$ then $G$ is union of three proper subgroups