On the size of planarly connected crossing graphs
Eyal Ackerman, Balázs Keszegh, Máté Vizer · DOAJ (DOAJ: Directory of Open Access Journals) · 2018
We prove that if an $n$-vertex graph $G$ can be drawn in the plane such that each pair of crossing edges is independent and there is a crossing-free edge that connects their endpoints, then $G$ has $O(n)$ edges. Graphs that admit such drawings are related to quasi-planar graphs and to maximal $1$-planar and fan-planar graphs.