21. Proved that the chromatic number of the graphs in the conjecture is at most, and improved this to. 22. It is in this sense that we view circular chromatic number as a refinement of the usual chromatic number. 23. It is in this sense that we view circular chromatic number as a refinement of the usual chromatic number . 24. It is a cubic graph with diameter 8, radius 7, chromatic number 2 and chromatic index 3. 25. The chromatic number of " G " is exactly 2; there is no vertex 1-coloring. 26. And its chromatic number is 4 : it can be colored using four colors, but not using only three. 27. It has chromatic number 3, chromatic index 3, radius 2, diameter 3 and edge-connected graph. 28. The Haj�s construction is a general method for constructing graphs with a given chromatic number , also due to Haj�s. 29. It has chromatic number 3, chromatic index 3, radius 6, diameter 6 and edge-connected graph. 30. He showed that in case of outerplanar graph of maximum degree 4, the incidence chromatic number is not 5.
