Eric Dinerstein, David Olson, et al. (2017). An Ecoregion-Based Approach to Protecting Half the Terrestrial Realm, BioScience, Volume 67, Issue 6, June 2017, Pages 534–545, [2]
worldwildlife.org
"Terrestrial Ecoregions of the World". World Wildlife Fund. Accessed 25 April 2020. [1]