New Scientist (367):558, November 28, 1963
Sir, —S. A. Gregory, in his letter (15 August) on "Literature in decay", gives once more an often repeated, but completely unsubstantiated statement that "it is unusual for scientific and technical references to be pursued for more than 30 years back".
Your readers may be interested in the following facts, based on the 1.4 million references processed for the Science Citation Index earlier this year. About one-tenth of the references were to papers published over 30 years ago. If this seems small in comparison to the total, keep in mind that only a small percentage of the extant scientific literature existed over 30 years ago. It is a fair approximation to state that the average scientific paper is cited once each year. While age of citation does have some effect, it is not as drastic as we had previously thought.
Institute for Scientific Information,
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