Redner replies: I appreciate the letters written about my article. To amplify a comment in the letter by J. C. Phillips, only 3 of the top 100 cited articles as of June 2003 are experimental.
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From my myopic theorist’s perspective, it is also surprising that all these articles are old. Given that physics is an experimental science, the caveats of Phillips and of Bryan Suits are well taken.
The letter by Rustum Roy makes the good point that citations can get transmuted to acronyms or to no citations at all, as in the case of the polymerase chain reaction. More dramatically, the most important scientific advances ultimately get incorporated into the canon; thus we never cite Isaac Newton when writing F = ma. It is clear that citations alone are an imperfect measure of the scientific importance of a paper, and one must proceed with caution in developing citation-based productivity measures.