APA (7th ed.) Citation

Porter, D., & Prince, D. (2004). Frommer's Portugal (18th ed.). Wiley.

Chicago Style (17th ed.) Citation

Porter, Darwin, and Danforth Prince. Frommer's Portugal. 18th ed. Hoboken, NJ: Wiley, 2004.

MLA (9th ed.) Citation

Porter, Darwin, and Danforth Prince. Frommer's Portugal. 18th ed. Wiley, 2004.