Four Color Theorem/Also known as

Four Color Theorem: Also known as

In British English, the Four Color Theorem is spelled Four Colour Theorem.

Some sources hyphenate: Four-Colo(u)r Theorem.

Some sources continue to refer to it as the Four Colo(u)r problem (with or without the hyphen), acknowledging the controversial nature of its supposed proof.

Sources

• 1998: David Nelson: The Penguin Dictionary of Mathematics (2nd ed.) ... (previous) ... (next): four-colour problem
• 2008: David Nelson: The Penguin Dictionary of Mathematics (4th ed.) ... (previous) ... (next): four-colour problem
• 2014: Christopher Clapham and James Nicholson: The Concise Oxford Dictionary of Mathematics (5th ed.) ... (previous) ... (next): chromatic number
• 2014: Christopher Clapham and James Nicholson: The Concise Oxford Dictionary of Mathematics (5th ed.) ... (previous) ... (next): Four Colour Theorem