Abstract
Hovey [11] called a graph G is A - cordial where A is an additive Abelian group and f : V (G) -> A is a labeling of the vertices of G with elements of A such that when the edges of G are labeled by the induced labeling f : E(G) -> A by f* (xy) = f(x) f(y) then the number of vertices (resp. edges) labeled with a and the number of vertices (resp. edges) labeled with b differ by at most one for all a, b is an element of A. When A = Z(k) we call a graph G is k - cordial instead of Z(k) - cordial. In this paper, we give a sufficient condition for the join of two k - cordial graphs to be k - cordial and we give also a necessary condition for certain Eulerian graphs to be k - cordial when k is even and finally we complete the characterization of the 4 cordiality of the complete tripartite graph.