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The present list contains dates of samples measured since our previous list (R., 1971, v. 13, p. 135–140). As before, age calculations are based on the Libby half-life 5568 ± 30 yr, and reported in years before 1950. The modern standard is 0.950 of the activity of NBS oxalic acid, giving a net counting rate of 21.68cpm. The background count is measured by a series of inactive samples such as marble, anthracite, petroleum coke, and old natural methane. Background count of these samples give adoi:10.1017/s0033822200001314 fatcat:tpjcd6mjgrb5dg43oiqh544jke