How to construct proportional Venn diagrams

I found this great software for drawing proportional Venn diagrams (with either circles or ellipses for better accuracy). Very easy to use!

Here's their PLOS One paper too:

http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0101717 http://www.eulerdiagrams.org/eulerAPE/

#Venn