Clark, Fay E. “Marine Mammal Cognition and Captive Care: A Proposal for Cognitive Enrichment in Zoos and Aquariums”. Journal of Zoo and Aquarium Research 1, no. 1 (July 24, 2013): 1–6. Accessed June 23, 2024. https://www.jzar.org/jzar/article/view/19.