“…The bipartite Kneser graph H(n, 1) has V as its vertex-set, and two vertices v, w are adjacent if and only if v ⊂ w or w ⊂ v. It is easy to see that H(n, 1) is a bipartite graph of diameter 3. Some of properties of the graph H(n, 1) and a generalization of it have been appeared in [11,13,14]. We can easyly show that H(n, 1) is a design graph with parameters (n, n − 1, n − 2).…”