E)$ be a cubic graph with chromatic index 4 and $c:E→{1
2
3
4}$ a proper 4-edge-coloring.Let $E-i={e∈E|c(e)=i}$ and $o(c)=%min%{|E-i||i=1
2
3
4}.$ Denote by $C(G)$ all the proper 4-edge-colorings of $G$ and $m(G)= %min% [DD(X] c∈C(G) {o(c)}$ is defined to be the color-character of $G.$ In this paper
we prove that $m(G)$ is a constant under the $Δ-$reduction.
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references
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