APA (7th ed.) Citation

Clay, J. C., & Herford, O. (2007). Happy Days. Project Gutenberg.

Chicago Style (17th ed.) Citation

Clay, John Cecil, and Oliver Herford. Happy Days. Project Gutenberg, 2007.

MLA (9th ed.) Citation

Clay, John Cecil, and Oliver Herford. Happy Days. Project Gutenberg, 2007.

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