The power-law distribution and the Garfield's Law of Concentration of journal citation have long been verified by empirical data. As a relatively new type of reference, the URL references are cited more and more frequently in the scientific papers and their distribution is proved to fit for the Garfield's Law of Concentration too. In this article, we collect three URL references datasets extracted from papers written by researchers belonging to three big research groups: Chinese Academy of Sciences, Max Planck Institute, and the whole Chinese scientific researchers. Through the curve-fitting with SPSS and contrast the results with the judgment standard of power-law distribution, we verify that there also exists power-law distribution in the citation frequency of hostnames in these three URL references datasets. And our experimental results show that the range of power exponent in the journal references and the URL references are different. Started from the concrete empirical procedures and the final experimental results, we analyze four factors that may lead to this difference between journal references and URL references: the sample size, the sampling method, the concentration of citation and the type property of citation.
Egghe, L2005Power laws in the information production process: Lotkaian informetricsElsevierAmsterdam.
Power laws in the information production process: Lotkaian informetrics
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