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2. The Air Force computer program acquisition concept;Ratynski;SJCC,1967
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4. O. L., Williamson, G. G. Dorris, A. J. Ryberg, and W. E. Straight: Development studies of a software reliability program, NASA report, March 1970.
5. B. W. Boehm: Some information processing implications of Air Force space missions in the 1970's, Astronautics and Aeronautics, January 1971.