Fig 3: Regression from the numbers of authors on the quality richness.
<a href="https://en.wikibooks.org/wiki/User:Rosskurator~enwikibooks" class="extiw" title="wikibooks:User:Rosskurator~enwikibooks">Rosskurator~enwikibooks</a> at <a href="https://en.wikibooks.org/wiki/" class="extiw" title="wikibooks:">English Wikibooks</a>
<span class="int-own-work" lang="">Own work by the original uploader</span>