APA (7th ed.) Citation

Darwin, C. (1997). The Voyage of the Beagle. Project Gutenberg.

Chicago Style (17th ed.) Citation

Darwin, Charles. The Voyage of the Beagle. Project Gutenberg, 1997.

MLA (9th ed.) Citation

Darwin, Charles. The Voyage of the Beagle. Project Gutenberg, 1997.

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