Biconnected Graph
[Basic Concepts]

The graphs we discuss below are all about loopfree undirected ones. Figure 1. The graph G that is not biconnected 
[Example] Graph G in Figure 1:

Figure 2. Depthfirst panning tree of the graph G 
[Step 1.]  Find the depthfirst spanning tree T for G 
[Step 2.]  Add back edges in T  
[Step 3.]  Determine DNF(i) and L(i)  
[Step 4.]  Vertex i is an articulation point of G if and only if eather: 
[Example] The DFN(i) and L(i) of Graph G in Figure 1 are: 
[Program]
