APA (7th ed.) Citation

Allen, R. (2007). The penguin english dictionary. Penguin Books.

Chicago Style (17th ed.) Citation

Allen, Robert. The Penguin English Dictionary. Penguin Books, 2007.

MLA (8th ed.) Citation

Allen, Robert. The Penguin English Dictionary. Penguin Books, 2007.

Warning: These citations may not always be 100% accurate.