APA (7th ed.) Citation

Butler, S. (2001). God the Known and God the Unknown. Project Gutenberg.

Chicago Style (17th ed.) Citation

Butler, Samuel. God the Known and God the Unknown. Project Gutenberg, 2001.

MLA (9th ed.) Citation

Butler, Samuel. God the Known and God the Unknown. Project Gutenberg, 2001.

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