Henry Ernest Dudeney/Modern Puzzles/140 - The Four-Colour Map Theorem/Historical Note

Historical Note on 's Modern Puzzles No. $140$ - The Four-Colour Map Theorem

 * For just about $50$ years various mathematicians, including, , , , , , , and many others have attempted to prove the truth of this theorem,
 * and in a long and learned article in the  for July-August, $1923$, Professor, of the University of Illinois, states that "the problem is still unsolved."''