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V G to the set of non-negative integers such that adjacent vertices get numbers at least two apart, and vertices at distance two get distinct numbers. The (2,1) L -labelling number denoted by 2,1 ( ) G λ of G is the minimum range of labels over all such labelling. In this article, it is shown that, for a circular-arc graph G , the upper bound of 2,1 ( ) G λ is 3ω ∆ +, where ∆ and ω represents the maximum degree of the vertices and size of maximum clique respectively.

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