Figure 2

The probability \(\pmb{P_{i\to j}(p^{*})}\) to observe a citation between two articles whose bibliographies overlap is statistically significant at the threshold value \(\pmb{p^{*}}\) . Notice that \(P_{i\to j}(p^{*})\) increases as the statistical threshold \(p^{*}\) decreases. That is, citations between pairs of articles characterised by a highly significant overlap tend to occur with a higher likelihood than citations between articles whose reference lists are not significantly similar. The inset shows how the number of pairs of articles characterised by a statistically significant similarity at a given threshold \(p^{*}\) varies with \(p^{*}\).