Darwin, C. (1872). Origin of species by means of natural selection or the preservation of favoured races in the struggle for life and the descent of man and selection in relation to sex (6th ed.). Modern Library.

Darwin, Charles. Origin of Species by Means of Natural Selection or the Preservation of Favoured Races in the Struggle for Life and the Descent of Man and Selection in Relation to Sex. 6th ed. New York: Modern Library, 1872.

Darwin, Charles. Origin of Species by Means of Natural Selection or the Preservation of Favoured Races in the Struggle for Life and the Descent of Man and Selection in Relation to Sex. 6th ed. Modern Library, 1872.