Talk:Cartesian Product of Countable Sets is Countable/Corollary/Proof 2

According to the definition of countable, only showing that there exists such an injection is enough. --kc_kennylau (talk) 23:50, 19 September 2014 (UTC)


 * But without an indication that $f$, $g$ and $r$ are injections, the proof is meaningless. --prime mover (talk) 07:24, 20 September 2014 (UTC)