Distributions of number of and average number of accession numbers cited per article over time.

<p>The graphs show the number of (a) and the average number of (b) ENA, PDB and UniProt accession numbers cited per article according to publication year (in the OA-ePMC). Data from 2012 is excluded as it is not a complete year. In <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0063184#pone-0063184-g005" target="_blank">Figure 5(b)</a>, for a given year and database, average value is calculated by using articles containing accession number citations only. Text-mined results are used together with the publisher-annotated data to generate the graphs.