Abstract
Incidence coloring of a graph G is a mapping from the set of incidences to a color-set C such that adjacent incidences of G are
assigned distinct colors. Since 1993, numerous fruitful results as regards incidence coloring have been proved. However, some of
them are incorrect.We remedy the error of the proof in [R.A. Brualdi, J.J.Q. Massey, Incidence and strong edge colorings of graphs,
Discrete Math. 122 (1993) 51–58] concerning complete bipartite graphs. Also, we give an example to show that an outerplanar
graph with D 4 is not 5-incidence colorable, which contradicts [S.D. Wang, D.L. Chen, S.C. Pang, The incidence coloring
number of Halin graphs and outerplanar graphs, Discrete Math. 256 (2002) 397–405], and prove that the incidence chromatic
number of the outerplanar graph with 7 is C1. Moreover, we prove that the incidence chromatic number of the cubic Halin
graph is 5. Finally, to improve the lower bound of the incidence chromatic number, we give some sufficient conditions for graphs
that cannot be . C 1/-incidence colorable.
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