1. such that |S ? V (G i )| = 3. By Lemma 4.1, (n -1) IDSTs can be obtained in BP n . Case 3. There exist different integers {i, j} ? [[n]] such that |S ? V (G i )| = 2 and |S ? V (G j )| = 2. According to Lemma 5.1, (n -1) IDSTs can be obtained in BP n . Case 4. There are different integers i;Then T 1 , � � � , T N-2;|S ? V (G i )| ? 1. By Lemma