• Are classic references cited first? An analysis of citation order within article sections

      Thelwall, Mike (Springer, 2019-06-07)
      Early citations within an article section may have an agenda-setting role but contribute little to the new research. To investigate whether this practice may be common, this article assesses whether the average impact of cited references is influenced by the order in which they are cited within article sections. This is tested on 1,683,299,868 citations to 41,068,375 unique journal articles from 1,470,209 research articles in the PubMed Open Access collection, split into 22 fields. The results show that the first cited article in the Introduction and Background have much higher average citation impacts than later articles, and the same is true to a lesser extent for the Discussion and Conclusion in most fields, but not the Methods and Results. The findings do not prove that early citations are less central to the citing article but nevertheless add to previous evidence suggesting that this practice may be widespread. It may therefore be useful to distinguish between initial introductory citations when evaluating citation impact, or to use impact indicators that implicitly or explicitly give less weight to the citation counts of highly cited articles.
    • Can Google Scholar and Mendeley help to assess the scholarly impacts of dissertations?

      Kousha, Kayvan; Thelwall, Mike (Elsevier, 2019-03-11)
      Dissertations can be the single most important scholarly outputs of junior researchers. Whilst sets of journal articles are often evaluated with the help of citation counts from the Web of Science or Scopus, these do not index dissertations and so their impact is hard to assess. In response, this article introduces a new multistage method to extract Google Scholar citation counts for large collections of dissertations from repositories indexed by Google. The method was used to extract Google Scholar citation counts for 77,884 American doctoral dissertations from 2013 to 2017 via ProQuest, with a precision of over 95%. Some ProQuest dissertations that were dual indexed with other repositories could not be retrieved with ProQuest-specific searches but could be found with Google Scholar searches of the other repositories. The Google Scholar citation counts were then compared with Mendeley reader counts, a known source of scholarly-like impact data. A fifth of the dissertations had at least one citation recorded in Google Scholar and slightly fewer had at least one Mendeley reader. Based on numerical comparisons, the Mendeley reader counts seem to be more useful for impact assessment purposes for dissertations that are less than two years old, whilst Google Scholar citations are more useful for older dissertations, especially in social sciences, arts and humanities. Google Scholar citation counts may reflect a more scholarly type of impact than that of Mendeley reader counts because dissertations attract a substantial minority of their citations from other dissertations. In summary, the new method now makes it possible for research funders, institutions and others to systematically evaluate the impact of dissertations, although additional Google Scholar queries for other online repositories are needed to ensure comprehensive coverage.