APA (7th ed.) Citation

Kjelgaard, J. (2012). Double Challenge. Project Gutenberg.

Chicago Style (17th ed.) Citation

Kjelgaard, Jim. Double Challenge. Project Gutenberg, 2012.

MLA (9th ed.) Citation

Kjelgaard, Jim. Double Challenge. Project Gutenberg, 2012.

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