I'm trying to prove $|A| = |B|$, and I have two injective functions $f:A \to B$ and $g:B \to A$. Is this enough proof for a bijection, which would prove $|A| = |B|$? It seems logical that it is, but I can't find a definitive answer on this.
All I found is this yahoo answer:
One useful tool for proving that two sets admit a bijection between them is a theorem which says that if there is an injective function $f: A \to B$ and an injective function $g: B \to A$ then there is a bijective function $h: A \to B$. The theorem doesn't really tell you how to find $h$, but it does prove that $h$ exists. The theorem has a name, but I forget what it is.
But he doesn't name the theorem name and the yahoo answers are often unreliable so I don't dare to base my proof on just this quote.