- American Museum of Natural History http://www.amnh.org/exhibitions/past-exhibitions/darwin/evolution-today/how-does-natural-selection-work 'How Does Natural Selection Work?' Retrieved 30 March 2015
- Wikipedia http://en.wikipedia.org/wiki/Charles_Darwin 'Charles Darwin' Retrieved 31 March 2015
- University of California Museum of Paleontology http://evolution.berkeley.edu/evolibrary/article/history_14 'Natural Selection: Charles Darwin & Alfred Russel' Retrieved 31 March 2015
- WestOne http://tle.westone.wa.gov.au/content/file/c0a7f9da-2dc9-b549-578a-0f1a8921d148/1/bio_science_3b.zip/content/003_mechanisms/page_03.htm 'Selective Pressures' Retrieved 31 March 2015
- Lofts, Graeme & Evergreen, Merrin (2015) "Chapter 3.2" Science Quest 10 for the Australian Curriculum (pp. 78-81). Australia: John Wiley & Sons Australia
- Lofts, Graeme & Evergreen, Merrin (2015) "Chapter 3.4" Science Quest 10 for the Australian Curriculum (pp. 89-91). Australia: John Wiley & Sons Australia