Graceful centers of graceful graphs and universal graceful graphs.
Makadia, H. M.
Karavadiya, H. M.
Kaneria, V. J.
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.