A comment to: Two classes of edge domination in graphs

Let G be a graph of order n and denote the signed edge domination number of G. In B. Xu, Two classes of edge domination in graphs, Discrete Appl. Math. 154 (2006) 1541-1546] it was proved that for any graph G of order n, . But the method given in the proof is not correct. In this paper we give an example for which the method of proof given in 1] does not work.