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Older values of the constants Archive of older articles and tables of values A 1969 set of recommended values of the basic constants and conversion factors of physics and chemistry from researchers at RCA Laboratories and the University of Pennsylvania are provided for historical reference below: Detailed description of the 1969 adjustment, including the covariance matrix of selected constants: B. N. Taylor, W. H. Parker, and D. N. Langenberg, Rev. Mod. Phys. 41(3), 375-496 (1969)    Return to Background information related to the constants.