APA (7th ed.) Citation

Le Guin, U. K. (1979). The Earthsea trilogy. Penguin Books.

Chicago Style (17th ed.) Citation

Le Guin, Ursula K. The Earthsea Trilogy. Harmondsworth, England ; Ringwood, Vic.: Penguin Books, 1979.

MLA (8th ed.) Citation

Le Guin, Ursula K. The Earthsea Trilogy. Penguin Books, 1979.