Finding all $\mathbb Z$-module homomorphisms $\mathrm{Hom}(\mathbb Z/n\mathbb Z, \mathbb Z/m\mathbb Z)$
136804
Computing $\mathrm{Hom}(\mathbb Z_n,\mathbb Z_m)$ as $\mathbb Z$-module
51334
Does there exist any surjective group homomorphism from $(\mathbb R^* , .)$ onto $(\mathbb Q^* , .)$?
144105
Ring homomorphism from $\mathbb Z$ to $\mathbb Z$ is always identity or $0$
114916
$\mathbb Z_{mn}$ isomorphic to $\mathbb Z_m\times\mathbb Z_n$ whenever $m$ and $n$ are coprime
157915
Isomorphism between the group $(\mathbb Z[x], +)$ and $(\mathbb Q_{>0}, .)$
64025
Ring homomorphisms from $\Bbb Q$ into a ring
40400
Finding an isomorphism between $\mathbb{Z}[i]/(7)$ and $\mathbb{Z}[\sqrt{-2}]/(7)$
5699
The number of ring homomorphisms from $\mathbb{Z}_m$ to $\mathbb{Z}_n$
145933
Localization commutes with Hom for finitely-generated modules
121246
Projective modules and $\hom(P,\cdot)$
28518
Hom of finitely generated modules over a noetherian ring
146341
Finding all ring homomorphisms from a field to itself
128701
Are $\mathbb{Q}$ or $\mathbb{Z}$ flat modules?
18343
Counting homomorphisms between $\Bbb Z$ and $\Bbb Z_n$ and also between $\Bbb Z_n$ and $\Bbb Q$
137029
Prove that $\operatorname{Hom}_{\Bbb{Z}}(\Bbb{Q},\Bbb{Z}) = 0$ and show that $\Bbb{Q}$ is not a projective $\Bbb{Z}$-module.
76391
What are all the homomorphisms between the rings $\mathbb{Z}_{18}$ and $\mathbb{Z}_{15}$?
34599
Number of ring homomorphisms from $\mathbb Z_{12}$ to $\mathbb Z_{28}$.