Sufficient Conditions for Graphs to Be Maximally 3-restricted Edge Connected

Let G=(V,E) be a connected graph.A graph G is called λ3-optimal,if λ3(G),where ξ3(G)=min{||:XV,|X|=3,G[X] is connected}.In this paper,we study the relation between R(G) and vertex number n,minimum degree δ,ξ3,and obtain a function.If R(G) is not more than the function,then G is λ3-optimal.