• [Wiki] http://en.wikipedia.org/wiki/Urocitellus_richardsonii.
• [AnAge] http://genomics.senescence.info/species/entry.php?species=Urocitellus_richardsonii.
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• [ZullRick1984] Zullinger, E. M., Ricklefs, R. E., Redford, K. H., and Mace, G. M. (1984). Fitting sigmoidal equations to mammalian growth curves. Journal of Mammalogy, 65(4):607--636.