Kuratowski's Lemma/Historical Note

Historical Note on Kuratowski's Lemma
published what is now known as Kuratowski's Lemma in $1922$, thinking it little more than a corollary of Hausdorff's Maximal Principle.

In $1935$, published his own equivalent, now known as Zorn's Lemma, acknowledging 's earlier work.

This later version became the more famous one.