Schematic illustration of the multiplication of two <a href="https://en.wikipedia.org/wiki/combinatorial_species" class="extiw" title="w:combinatorial species">combinatorial species</a>.
<a href="//commons.wikimedia.org/w/index.php?title=User:Byorgey&amp;action=edit&amp;redlink=1" class="new" title="User:Byorgey (page does not exist)">Brent Yorgey</a>
CC BY-SA 3.0
<span class="int-own-work" lang="en">Own work</span>. See the <a href="https://en.wikipedia.org/wiki/File_talk:Multiplication_of_combinatorial_species.svg#Source_code" class="extiw" title="w:File talk:Multiplication of combinatorial species.svg">source code</a>.