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, L 2005 Power laws in the information production process: Lotkaian informetrics Elsevier Amsterdam.
Egghe, L, Rousseau, R 2006 An informetric model for the Hirsch-index. Scientometrics 69 1 121–129 .
Fang, A. L., Gao, Q. S., & Zhang, S. Y. (2007). A study on the test of power-law distribution of citation network. Statistics and Decision, 14, 22–24 (In Chinese).
Garfield, E 1972 Citation analysis as a tool in journal evaluation. Science 178 4060 471–479 .
Hu, HB, Wang, L 2005 A brief history of power law distributions. Physics 34 12 889–896 (In Chinese).
Krashakov, SA, Teslyuk, AB, Shchur, LN 2006 On the universality of rank distributions of website popularity. Computer Networks 50 11 1769–1780 .
Larivière, V, Gingras, Y, Archambault, É 2009 The decline in the concentration of citation, 1900–2007. Journal of the American Society for Information Science and Technology 60 4 858–862 .
Li, Y. J., & Chen, Y. S. (2009). Survey analysis on the web citations of the periodicals on library science. Sci-Tech Information Development & Economy, 19 (6), 43–47 (In Chinese).
Liu, C. H. (2004). Evaluation of medical information resources on the Internet by citation analysis: A primary study. Chin J Med Libr Inf Sci, 13 (6), 58–60 (In Chinese).
Liu, ZM, An, MR, Zhang, CY 2005 Web citation's author analysis. Information Science 23 2 202–204 (In Chinese).
Liu, YX, Rao, IKR, Rousseau, R 2009 Empirical series of journal h-indices: The JCR category Horticulture as a case study. Scientometrics 80 1 59–74 .
Meng, L. S. (1982). Chinese Science Citation Analysis. Master's thesis, Library of Chinese Academy of Sciences, Beijing (In Chinese).
Pan, N 2006 An analysis of author of web citation from the core information science periodicals. Journal of Academic Library and Information Science 24 6 86–89 (In Chinese).
Price, DJ de Solla 1965 Networks of science paper. Science 149 3683 510–515 .
Price, DJ de Solla 1976 A general theory of bibliometric and other cumulative advantage processes. Journal of the American Society for Information Science 27 5–6 292–306 .
Redner, S 1998 How popular is your paper? An empirical study of the citation distribution. European Physical Journal B 4:131–134 .
W3C (1994). Uniform Resource Locators. http://www.w3.org/Addressing/rfc1738.txt. Accessed 4 Jan. 2011.
Wang, L 2008 Research on the distribution of the citations of social science-the statistical analysis of the 2005 JCR social science. Library Development 8:104–107 (In Chinese).
Wren, JD 2004 404 not found: the stability and persistence of URLs published in MEDLINE. Bioinformatics 20 5 668–672 .
Yang, SL, Ma, F, Song, YH, Qiu, JP 2010 A longitudinal analysis of citation distribution breadth for Chinese scholars. Scientometrics 85:755–765 .
Yang, SL, Qiu, JP, Xiong, ZY 2010 An empirical study on the utilization of web academic resources in humanities and social sciences based on web citations. Scientometrics 84:1–19 .
Ye, FY, Rousseau, R 2008 The power law model and total career h-index sequences. Journal of Informetrics 2:288–297 .
Ye, FY, Rousseau, R 2010 Probing the h-core: An investigation of the tail-core ratio for rank distributions. Scientometrics 84:431–439 .
Zhang, CY, An, MR, Wang, JF, Jiang, RZ 2004 Quantitative exploration of web citation. Journal of the China Society for Scientific and Technical Information 23 5 566–570 (In Chinese).