Вид треугольника Ленне
<a href="//commons.wikimedia.org/wiki/User:Hellerick" title="User:Hellerick">Hellerick</a>
CC BY-SA 4.0
<span class="int-own-work" lang="en">Own work</span>, based on <a rel="nofollow" class="external autonumber" href="http://www.berlin.de/mauer/zahlen_fakten/gebietsaustausch/index.de.html">[1]</a> and other sources