A lovely description! Fisk's is certainly the proof 'from the book' but Václav Chvátal perhaps deserves a mention as the first person to answer Klee's question? See http://www.theoremoftheday.org/Theorems.html#198

## A shout out for Chvátal

A lovely description! Fisk's is certainly the proof 'from the book' but Václav Chvátal perhaps deserves a mention as the first person to answer Klee's question? See http://www.theoremoftheday.org/Theorems.html#198