APA (7th ed.) Citation

Gude, K., & Duckworth, M. (1994). Proficiency masterclass: Student's book. Oxford University Press.

Chicago Style (17th ed.) Citation

Gude, Kathy, and Michael Duckworth. Proficiency Masterclass: Student's Book. Oxford: Oxford University Press, 1994.

MLA (9th ed.) Citation

Gude, Kathy, and Michael Duckworth. Proficiency Masterclass: Student's Book. Oxford University Press, 1994.