APA (7th ed.) Citation

Darlton, C. (1973). Challenge of the unknown (American ed.). Ace Books.

Chicago Style (17th ed.) Citation

Darlton, Clark. Challenge of the Unknown. American ed. New York: Ace Books, 1973.

MLA (9th ed.) Citation

Darlton, Clark. Challenge of the Unknown. American ed. Ace Books, 1973.