Figure 1 shows a red dot, our “article of interest.” It is cited by a number of articles (blue dots in the upper row), which we call “citing articles.” We can count the number of citations over time to our article of interest, yielding an “actual citation rate.” These citing articles not only cite our article of interest, but they also cite other articles, which we call the “co-citation network.” The corpus of co-citation network papers can be safely assumed to be reflective of the research field (or fields) of our article of interest. We can then calculate an estimated “field citation rate” by recording the citation rates of the journals that published the co-citation network papers.