1. Linnaeus C (1756) Systema Naturae, 9th edn. Theodor Haak, Leiden (Lugdunum Batavorum)
2. Darwin CR, Wallace AR (1858) On the tendency of species to form varieties; and on the perpetuation of varieties and species by natural means of selection. Journal of the Proceedings of the Linnean Society of London Zoology 3:46–50 [Read 1st. July, 1858]
3. Barlow N (1958) The autobiography of Charles Darwin 1809–1882. Collins, London, p 122
4. Virchow R (1858) Die Cellularpathologie in ihrer Begrundung auf physiologische und pathologische Gewebelehre. Berlin. Verlag von August Hirschwald, Berlin (English translation). Chance F (1860) Cellular Pathology. John Churchill, London. Reissued; Classics of Medicine Library, Birmingham. Alabama, 1979, pp 170–171
5. Swerdlow SH, Campo E, Harris NL et al (2008) WHO classification of tumors of the haematopoietic and lymphoid tissues. IARC. WHO, Geneva