Ballou, Jonathan D. 1989. "Inbreeding and outbreeding depression in the captive propagation of black-footed ferrets (Mustela nigripes)." in Conservation Biology and the Black-footed Ferret., edited by Seal, Ulysses S., Thorne, E. T., Bogan, M. A., and Anderson, S. H., 49–68. New Haven, CT: Yale Univ. Press.