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Johnson 1998, p. 41. Johnson, Luanne (March 1998). "A view from the 1960s: how the software industry began". IEEE Annals of the History of Computing. 20 (1): 36–42. doi:10.1109/85.646207.
Johnson 1998, p. 50. Johnson, Luanne (March 1998). "A view from the 1960s: how the software industry began". IEEE Annals of the History of Computing. 20 (1): 36–42. doi:10.1109/85.646207.