APA (7th ed.) Citation

Darwin, C., & Peckham, M. (1959). The origin of species: A variorum text. University of Pennsylvania Press.

Chicago Style (17th ed.) Citation

Darwin, Charles, and Morse Peckham. The Origin of Species: A Variorum Text. Philadelphia [Pa.]: University of Pennsylvania Press, 1959.

MLA (9th ed.) Citation

Darwin, Charles, and Morse Peckham. The Origin of Species: A Variorum Text. University of Pennsylvania Press, 1959.