Resumen de Graceful centers of graceful graphs and universal graceful graphs.

H. M. Makadia, H. M. Karavadiya, V. J. Kaneria

• In this paper we define graceful center of a graceful graph. We proved any graph G which admits α-labeling has at least four graceful centers. We also defined a new strong concept of universal graceful graph. Some results on ring sum of two graphs for their graceful labeling are proved.