(2,1)-Total Labelling of Trees
Suppose thatis a tree with. We know that .is called type 1 ifand type 2 if. In this paper, we give a sufficient condition for a tree withto be type 1.
H. N. Sun "(2,1)-Total Labelling of Trees", Key Engineering Materials, Vols. 474-476, pp. 2234-2238, 2011