(ZF) Existence of injection and surjection
40586
There exists an injection from $X$ to $Y$ if and only if there exists a surjection from $Y$ to $X$.
14994
Showing a function $f$ cannot be surjective
77944
Injective functions with intermediate-value property are continuous. Better proof?
5584
How strong is this second-order version of ZFC?
138258
What is the injective envelope of $\mathbb{Z}/n\mathbb{Z}$?
118189
Proving the pairing axiom from the rest of ZF
137982
Show that $\textbf{ZF}$ shows $\phi$ is $\Delta_1$
122814
Finite Sets, Equal Cardinality, Injective $\iff$ Surjective.
148500
Understanding this theorem and how to go about proving it surjectivity?
135282
How can I construct a sequence of injections $\langle f_\alpha\colon\alpha\to\omega\mid\alpha<\omega_1\rangle$ with a particular coherence property?
76974
What ZF axioms does Cantor's diagonal argument require?
73415
The reason why the existence of inaccessible cardinals cannot be proven in ZFC
25887
Definition of Dedekind-infinity: Bijection or Injections?
84114
Does there exist a surjective homomorphism from $(\mathbb R,+)$ to $(\mathbb Q,+)$ ?
93040
$f$ is surjective iff it has a right inverse: using the axiom of choice and errors in ProofWiki
21707
Constructing a Bijective function via an injective and surjective one.
146306
A continuous surjective function from $(0,1]$ onto $[0,1]$