“…Such identifying codes were introduced in Karpovsky, Chakrabarty and Levitin [11]. Many results have been obtained about the identifying codes, for instance in the triangular lattice, the square and king grids and the hexagonal mesh, see, e.g., [1][2][3][6][7][8][9][10], and their references. For the closely related problem of locating-dominating sets, in which the sets I(v) are required to be nonempty and pairwise different for v / ∈ C, we refer to [4,12,14,15].…”