Darwin, Charles. 1871. The Descent of Man, and selection in relation to sex. London: John Murray. Volume. 1. 1st edition. p 201 Bilimsel ırkçılık[1]
cambridge.org
Darwin, Charles (Temmuz 2009). "DIFFICULTIES OF THE THEORY". The Origin of Species: By Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life (İngilizce). 16 Haziran 2018 tarihinde kaynağından arşivlendi. Erişim tarihi: 15 Ağustos 2020.
Darwin, Charles (Temmuz 2009). "DIFFICULTIES OF THE THEORY". The Origin of Species: By Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life (İngilizce). 16 Haziran 2018 tarihinde kaynağından arşivlendi. Erişim tarihi: 15 Ağustos 2020.