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Annalisa Berta; Morgan Churchill; Robert W. Boessenecker (2018). “The Origin and Evolutionary Biology of Pinnipeds: Seals, Sea Lions, and Walruses”. Annual Review of Earth and Planetary Sciences. 46 (1): 203–228. Bibcode:2018AREPS..46..203B. doi:10.1146/annurev-earth-082517-010009.