APA (7th ed.) Citation

Gardner, M. (1989). Penrose tiles to trapdoor ciphers / Martin Gardner. Freeman.

Chicago Style (17th ed.) Citation

Gardner, Martin. Penrose Tiles to Trapdoor Ciphers / Martin Gardner. New York: Freeman, 1989.

MLA (9th ed.) Citation

Gardner, Martin. Penrose Tiles to Trapdoor Ciphers / Martin Gardner. Freeman, 1989.

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