• [Wiki] http://en.wikipedia.org/wiki/Sciurus_niger.
• [AnAge] http://genomics.senescence.info/species/entry.php?species=Sciurus_niger.
• [ADW] http://animaldiversity.org/accounts/Sciurus_niger/.
• [BrowYeag1945] Brown, L. G. and Yeager, L. E. (1945). Fox squirrels and gray squirrels in Illinois. Bull. Illinois Nat. Hist. Survey, 23(5):445--536.
• [Kooy2010] Kooijman, S. (2010). Dynamic Energy Budget theory for metabolic organisation. Cambridge Univ. Press, Cambridge.