Let 
be a finite, connected,
undirected graph with graph
diameter 
and graph distance 
between vertices 
and 
. A radio
labeling of a graph 
is labeling using distinct nonnegative integers such that 
for every pair of distinct vertices
, 
in the vertex set of 
. Then the radio number of 
, commonly denoted 
, is the smallest integer 
such that 
has a radio labeling 
with 
.
The radio number of path graphs 
and cycle graphs 
were determined by Liu and Zhu (2005). The following table
summarizes some known results for a number of special families of graphs.
for 
