APA (7th ed.) Citation

Haeckel, E., & Gadow, H. (2013). The Last Link Our Present Knowledge of the Descent of Man. Project Gutenberg.

Chicago Style (17th ed.) Citation

Haeckel, Ernst, and Hans Gadow. The Last Link Our Present Knowledge of the Descent of Man. Project Gutenberg, 2013.

MLA (9th ed.) Citation

Haeckel, Ernst, and Hans Gadow. The Last Link Our Present Knowledge of the Descent of Man. Project Gutenberg, 2013.

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