Spaulding, M., O'Leary, M. A., & Gatesy, J. (2009). Relationships of Cetacea (Artiodactyla) among mammals: increased taxon sampling alters interpretations of key fossils and character evolution. Plos one, 4(9), e7062. https://dx.doi.org/10.1371/journal.pone.0007062
jstor.org
Naylor, G. J., & Adams, D. C. (2001). Are the Fossil Data Really at Odds with the Molecular Data/Morphological Evidence for Cetartiodactyla Phylogeny Reexamined. Systematic Biology, 50(3), 444-453. https://www.jstor.org/stable/3070934