Maureen A. O'Leary, John Gatesy. Impact of increased character sampling on the phylogeny of Cetartiodactyla (Mammalia): combined analysis including fossils. „Cladistics”. 24 (4), s. 397–442, 2008. DOI: 10.1111/j.1096-0031.2007.00187.x. (ang.).
Michelle Spaulding, Maureen A. O'Leary, John Gatesy. Relationships of Cetacea (Artiodactyla) Among Mammals: Increased Taxon Sampling Alters Interpretations of Key Fossils and Character Evolution. „PLoS ONE”. 4 (9), s. e7062, 2009. DOI: 10.1371/journal.pone.0007062. (ang.).