Which n-Venn diagrams can be drawn with convex k-gons?

Jeremy Carroll Frank Ruskey Mark Weston Which n-Venn diagrams can be drawn with convex k-gons? http://arxiv.org/abs/cs/0512001 2005 CoRR abs/cs/0512001 db/journals/corr/corr0512.html#abs-cs-0512001 informal publication