Semigroup satisfying the cancellation property which cannot be embedded in a group
40743
When a semigroup can be embedded into a group
113925
Normal Subgroup Counterexample
152363
Cancellation in topological product
4383
Finitely generated monoids - how to show that there is not first order set axiomatizing them.
126771
Group element not taken to its inverse by any automorphism
111049
Groups with given automorphism groups
135241
Show that $\mathbb{Z}/n^2\mathbb{Z}$ is not isomorphic to other group
101735
A finite $p$-group cannot be simple unless it has order $p$
61373
A normal subgroup that is not a characteristic
114431
Monoids and Subgroups
24561
$\mathbb S_n$ as semidirect product
8746
Groups of order $pq$ without using Sylow theorems
94203
Examples for almost-semirings without absorbing zero
5089
An element of a group has the same order as its inverse
141642
Closure of a certain subset in a compact topological group
99538
Non-trivial groups pairwise non-isomorphic with isomorphic direct products
49162
Classify all groups with order $pq$, $p$ is not equal to $q$