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? 619-628 2007 37 Discrete & Computational Geometry 4 http://dx.doi.org/10.1007/s00454-007-1311-1 db/journals/dcg/dcg37.html#CarrollRW07