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This is a publication that does not have either 'Iowa' or 'curves' in its title that was actually published as Bulletin (Iowa State University Engineering Research Institute), #155 & #156, 1942, by Robley Winfrey, ISU Call Number: TA1 .Io8b. #155 is called "Depreciation of group properties." #156 is called "Condition percent tables for depreciation of unit and group properties." In 1967, the Engineering Research Institute published a reprint of Bulletin #125 entitled "Statistical analyses of industrial property retirements." John G. Russo validated the Iowa Curves in his Ph.D. thesis, "Revalidation of Iowa Type Survivor Curves," unpublished Ph.D. Dissertation, Iowa State University, Ames, Iowa 1978. ISU Call Number: ISU 1978 R921. There is also an article in the Engineering Economist, v. 26, no 1 (1980): 1-16, titled "Revalidation of Iowa Type Survivor Curves" by John G. Russo and H.A. Cowles, that compares data from the original bulletins with a new set of curves developed by John G. Russo as part of his Ph.D. thesis. ISU Call Number: HD28 .En325