APA (7th ed.) Citation

Twain, M. (1990). The man that corrupted Hadleyburg. Project Gutenberg.

Chicago Style (17th ed.) Citation

Twain, Mark. The Man That Corrupted Hadleyburg. Champaign, Ill: Project Gutenberg, 1990.

MLA (9th ed.) Citation

Twain, Mark. The Man That Corrupted Hadleyburg. Project Gutenberg, 1990.