APA (7th ed.) Citation

Title, Helfres, J., & Little, D. (2001). The valdemar companion. Penguin Books.

Chicago Style (17th ed.) Citation

Title, John Helfres, and Denise Little. The Valdemar Companion. USA: Penguin Books, 2001.

MLA (9th ed.) Citation

Title, et al. The Valdemar Companion. Penguin Books, 2001.