From the great Stan Kelly-Bootle : CHORUS Lemma three, very pretty, and the converse pretty too; But only God and Fermat know which of them is true. VERSE 1 When I studied number theory, I was happy in me prime, And all them wild conjectures, I knocked them two at a time, but... CHORUS VERSE 2 Last week, at supervision, Ken Ribet said to me: "Did you discover the deliberate mistake in lemma numberthree?" CHORUS VERSE 3 Lemma three it has puzzled mathematicians by the score, But Max Newman has engulfed it, and it won't be seen no more. CHORUS VERSE 4 Well, the axiom of choice, it is very clear to me: If you wanna choose a lemma, boys, then don't choose lemma three, for... CHORUS VERSE 5 And it's black and white together, we shall not be moved, But the four-color theorem, it hasn't yet been proved CHORUS Lemma three, very pretty, and the converse pretty too; But only God and Andrew know which of them is true. (Yes, both myself and the author know the four-colour...