See <a href="https://en.wikipedia.org/wiki/2-category" class="extiw" title="w:2-category">w:2-category</a>.
<a href="//commons.wikimedia.org/wiki/User:Incnis_Mrsi" title="User:Incnis Mrsi">Incnis Mrsi</a> (<a href="//commons.wikimedia.org/wiki/User_talk:Incnis_Mrsi" title="User talk:Incnis Mrsi"><span class="signature-talk">talk</span></a>)
2012-05-15
<span class="int-own-work" lang="en">Own work</span>