“…Further, by lemma 1, an HSB of size two constructed by algorithm Symmetric_Switch_Block is universal. (If) For an even V, by lemma 5, we can decompose a vector n ¼ (n 1,2 , n 1,3 , y, n 1,6 , n 2,3 , y, n 2,6 , n 3,4 , y, n 3,6 , n 4,5 , n 4,6 , n 5,6 ) into V/2 sub-RRVs n i ¼ (n i, (1,2) , n i, (1,3) , y, n i, (1,6) , n i, (2,3) , y, n i, (2,6) , n i, (3,4) , y, n i, (3,6) , n i, (4,5) , n i, (4,6) , n i, (5,6) ), where i ¼ 1,2, y, V/2, such that each sub-RRV satisfies the following set of inequalities:…”