Minimal visibility graphs (Q2639649)

Given n nonintersecting line segments in the plane, no three endpoints of which are colinear, the visibility graph generated by these n segments consists of the n segments and all segents formed by joining those endpoints of the n segments that can see each other. The authors give an alternative proof for the following result: The visibility graph of a set of n nonintersecting line segments in the plane contains at least 5n-4 edges.