Quasinormal subgroup which is not nomal
112263
an example for $\pi$-quasinormal subgroup but is not normal
2761
If $S$ is a nonempty subset of group $G$, then $S^{|G|}$ is a subgroup of $G$.
55178
When there is a unique Sylow p-subgroup it is normal, does this mean that non-unique p-subgroups are not normal?
57227
Maximal normal $\pi$-subgroups and torsion subgroups
10602
Monotone Union of subgroups being subgroup
57883
Example of a Subgroup That Is Not Normal
75590
How many normal subgroups does a non-abelian group $G$ of order $ 21$
91874
Existence of finite indexed normal subgroup for a given finite indexed subgroup.
124732
Finding a nonempty subset that is not a subgroup
92493
If $G$ is non-abelian, then $Inn(G)$ is not a normal subgroup of the group of all bijective mappings $G \to G$
153797
Is a quotient group a subgroup?
2767
Subgroups of the Klein-4 Group
35401
Examples of finite groups that are not a semidirect product
23941
Normal Subgroups that Intersect Trivially
86872
normalized subgroup by another subgroup
141265
Finding a normal and not normal subgroup of $S_3$
89508
Existence of normal subgroups for a group of order $36$