Radio numbers for generalized prism graphs

A radio labeling is an assignment c : V (G) ! N such that every distinct pair of vertices u,v satisfies the inequality d(u,v )+ |c(u) c(v) |diam(G) + 1. The span of a radio labeling is the maximum value of c. The radio number of G, rn(G), is the minimum span over all radio labelings of G. Generalized prism graphs, denoted Zn,s, s 1, n s, have vertex set {(i,j)|i =1 ,2 and j =1 ,...,n} and edge set