1. Graph Theory with Applications;Bondy,1976
2. Problem Session;Erdös,1991
3. posed this problem as the topic of a project of the course Graph Theory (Math. 776);Griggs,1990
4. The number of hexagons and the simplicity of geodesics on certain polyhedra;Grünbaum;Canad. J. Math.,1963
5. Planar graphs with few vertices of small degree;Lin,1993