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jstor.org
Cloud, Jr., Preston E. (1948). «Some problems and patterns of evolution exemplified by fossil invertebrates». Evolution. 2 (4): 322–350. JSTOR2405523. PMID18122310. doi:10.2307/2405523
nasonline.org
Crowell, John C. (1995). «Preston Cloud September 26, 1912–January 16, 1991»(PDF). Biographical Memoir of the National Academy of Sciences. National Academies Press. pp. 43–63. Consultado em 7 de setembro de 2014