APA (7th ed.) Citation

Gamma, E. (1995). Design patterns: Elements of reusable object-oriented software. Addison-Wesley.

Chicago Style (17th ed.) Citation

Gamma, Erich. Design Patterns: Elements of Reusable Object-oriented Software. Reading, Mass: Addison-Wesley, 1995.

MLA (9th ed.) Citation

Gamma, Erich. Design Patterns: Elements of Reusable Object-oriented Software. Addison-Wesley, 1995.