APA (7th ed.) Citation

Ball, R. S. (2008). The Story of the Heavens. Project Gutenberg.

Chicago Style (17th ed.) Citation

Ball, Robert S. The Story of the Heavens. Project Gutenberg, 2008.

MLA (9th ed.) Citation

Ball, Robert S. The Story of the Heavens. Project Gutenberg, 2008.

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