The <a href="https://en.wikipedia.org/wiki/complete_graph" class="extiw" title="w:complete graph">complete graph</a> on 4 vertices.
<a href="//commons.wikimedia.org/wiki/User:Dbenbenn" title="User:Dbenbenn">David Benbennick</a> wrote this file.
<span class="int-own-work" lang="en">Own work</span>