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Original Repository. Alan Mason Chesney Medical Archives. Daniel Nathans Collection. 12640. Periodical. Brockman, William W., and Daniel Nathans. "The Isolation of Simian Virus 40 Variants with Specifically Altered Genomes." Proceedings of the National Academy of Sciences of the United States of America 71, 3 (March 1974): 942-946. Article. 5 Images.. Proceedings of the National Academy of Sciences of the United States of America