^Primack, Richard (2014). Essentials of Conservation Biology. Sunderland, MA USA: Sinauer Associates, Inc. Publishers. pp. 217–245. ISBN 9781605352893.
^Ceballos, G.; Ehrlich, A. H.; Ehrlich, P. R. (2015). The Annihilation of Nature: Human Extinction of Birds and Mammals. Baltimore, Maryland: Johns Hopkins University Press. pp. 135 ISBN 1421417189 – via Open Edition.