Do two injective functions prove bijection? 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.

Yes this is true, it is called Cantor–Bernstein–Schroeder theorem.
