Fig. 4

Central nodes of 10-year time window rolling from year to year. The x-axis indicates time windows from 1980–1989 to 2004–2013, except for the first column labeled “ALL”, which is the all-year condition. The y-axis indicates the nodes, i.e. IPC subclasses, ordered in IPC index. Colored blocks indicate central nodes in a time window using at least one referencing method: Green represents central nodes both methods have in common, red for those central only by referring to the initial year, and yellow for those central only by referring to the previous year