... appear.[2]G.D.Cohen,I.Honkala,S.LitsynandA.Lobstein:Covering Codes, Elsevier,1997.[3] M.G.Karpovsky,K.ChakrabartyandL.B.Levitin: Onanewclassofcodes for identifying vertices in graphs, IEEE Trans. Inform. Th., vol. 44, ... vertex of degreezero.Since, by symmetry, one element in C2produces two vertices with degree zero or New Bounds for Codes Identifying Vertices in GraphsG´erard Cohencohen@inf.enst.frIiro Honkalahonkala@utu.fiAntoine ... Butthis identifying code is not optimal. Codewords can be deleted without losing the identifying property. We obtain the code of figure 9. Hence :Theorem 3.1The minimum density of an identifying...