APA (7th ed.) Citation

Vacca, J. R. (2005). The World's 20 greatest unsolved problems. Prentice Hall.

Chicago Style (17th ed.) Citation

Vacca, John R. The World's 20 Greatest Unsolved Problems. New Jersey: Prentice Hall, 2005.

MLA (9th ed.) Citation

Vacca, John R. The World's 20 Greatest Unsolved Problems. Prentice Hall, 2005.