APA (7th ed.) Citation

Northrop, E. P. (1944). Riddles in mathematics: A book of paradoxes. Penguin Books.

Chicago Style (17th ed.) Citation

Northrop, Eugene P. Riddles in Mathematics: A Book of Paradoxes. Harmondsworth: Penguin Books, 1944.

MLA (8th ed.) Citation

Northrop, Eugene P. Riddles in Mathematics: A Book of Paradoxes. Penguin Books, 1944.

Warning: These citations may not always be 100% accurate.