• [Wiki] http://en.wikipedia.org/wiki/Psammobates_geometricus.
• [Baar1995] Baard, E. H. W. (1995). Growth, age at maturity and sexual dimorphism in the geometric tortoise, Psammobates geometricus. The Journal of the Herpetological Association of Africa, 44(1):10--15. doi:10.1080/04416651.1995.9650383.
• [Kooy2010] Kooijman, S. (2010). Dynamic Energy Budget theory for metabolic organisation. Cambridge Univ. Press, Cambridge.