 Anthony William Fairbank Edwards constructed a series of Venn diagrams for higher numbers of sets by segmenting the surface of a sphere, which became known as Edwards–Venn diagrams.For example, three sets can be easily represented by taking three hemispheres of the sphere at right angles ("x" = 0, "y" = 0 and "z" = 0).A fourth set can be added to the representation by taking a curve similar to the seam on a tennis ball, which winds up and down around the equator, and so on.