A graph with edges is said to be harmonious, if there is an injection from the vertices of to the group of integers modulo such that when each edge is assigned the label (mod ), the resulting edge labels are distinct. In this paper, we study the existence of harmonious labeling for the corona graphs of a cycle and a graph and for the corona graph of and a tree.
"On Harmonious Labeling of Corona Graphs." J. Appl. Math. 2014 1 - 4, 2014. https://doi.org/10.1155/2014/627248