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 
