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  • × author_ss:"Raan, A.F.J. van"
  • × theme_ss:"Citation indexing"
  1. Raan, A.F.J. van: Self-citation as an impact-reinforcing mechanism in the science system (2008) 0.00
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    Abstract
    Previous research has demonstrated that lower performance groups have a larger size-dependent cumulative advantage for receiving citations than do top-performance groups. Furthermore, regardless of performance, larger groups have less not-cited publications. Particularly for the lower performance groups, the fraction of not-cited publications decreases considerably with size. These phenomena can be explained with a model in which self-citation acts as a promotion mechanism for external citations. In this article, we show that for self-citations, similar size-dependent scaling rules apply as for citations, but generally the power law exponents are higher for self-citations as compared to citations. We also find that the fraction of self-citations is smaller for the higher performance groups, and this fraction decreases more rapidly with increasing journal impact than that for lower performance groups. An interesting novel finding is that the variance in the correlation of the number of self-citations with size is considerably less than the variance for external citations. This is a clear indication that size is a stronger determinant for self-citations than it is for external citations. Both higher and particularly lower performance groups have a size-dependent cumulative advantage for self-citations, but for the higher performance groups only in the lower impact journals and in fields with low citation density.
  2. Raan, A.F.J. van: ¬The influence of international collaboration on the impact of research results (1998) 0.00
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    Abstract
    There is an ongoing discussion on the influence of international collaboration on impact as measured by citation based indicators. Collaboration generally involves more authors than 'no collaboration' work and it is obvious that the phenomenon of self citation will be stronger (there are more authors to cite themselves). Thus it can be seen as an important 'amplifier' of measured impact. Asserts, however, that this effect should not be considered as the only or even major explanation of higher impact in the comparison between 'no collaboration' and international collaboration. Using data of an extensive bibliometric study of astronomical research in the Netherlands, proves that higher rates of self citation in international collaboration do not play any significant role as 'impact amplifier'. The central point is that proper impact measurement must involve corrections for self citations