1. Askenasy E (1872) Beiträge zur Kritik der Darwin’schen Lehre. Engelmann, Leipzig
2. Aveling EB (1887) Die Darwin’sche Theorie. J.H.W. Dietz, Stuttgart (orig. The Darwinian theory: Its meaning, difficulties, evidence, history, London, Progressive Publishing Company, 1884)
3. Baehni C (1955) Correspondance de Charles Darwin et d’Alphonse de Candolle. Gesnerus 12:109–156
4. Bailey LH (1896a) The survival of the unlike. Proc Am Philos Soc 35:88–111
5. Bailey LH (1896b) The survival of the unlike. A collection of evolution essays suggested by the study of domestic plants. Macmillan, London