1. Algorithmic Graph Theory and Perfect Graphs;Golumbic,1980
2. Set-packing and threshold graphs;Chvàtal,1973
3. F.T. Boesch and Z. Bogdanowicz, The minimum number of spanning trees in a connected graph, (verbal communication).
4. Graphs with the maximum number of adjacent pairs of edges;Ahlswede;Acta Math. Acad. Sci. Hungar.,1978
5. The neighborhood inclusion digraphs of trees;Boesch,1987