APA (7th ed.) Citation

Darwin, C. (2011). The Descent of Man and Selection in Relation to Sex, Vol. I. Project Gutenberg.

Chicago Style (17th ed.) Citation

Darwin, Charles. The Descent of Man and Selection in Relation to Sex, Vol. I. Project Gutenberg, 2011.

MLA (9th ed.) Citation

Darwin, Charles. The Descent of Man and Selection in Relation to Sex, Vol. I. Project Gutenberg, 2011.

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