Equivalence of results from two citation analyses: Thomson ISI’s Citation Index and Google’s Scholar service

Citation counts were performed across a wide range of disciplines using both the Thomson ISI files and Google Scholar, and shown to lead to essentially the same results, in spite of their different methods for identifying citing sources. This has strong implications for future citation analyses, and the many promotion, tenure and funding decisions based thereon, notably because ISI products are rather costly, while Google Scholar is free.