APA (7th ed.) Citation

Guy, R. K. (1981). Unsolved problems in number theory (1. print.). Springer.

Chicago Style (17th ed.) Citation

Guy, Richard K. Unsolved Problems in Number Theory. 1. print. New York [u.a.]: Springer, 1981.

MLA (9th ed.) Citation

Guy, Richard K. Unsolved Problems in Number Theory. 1. print. Springer, 1981.