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2. Food webs and the dimensionality of trophic niche space;Cohen;Proc. Nat. Acad. Sci.,1977
3. Food Webs and Niche Space;Cohen,1978
4. Characterization of n-path graph and of graphs having nth root;Escalante;J. Combin. Theory (B),1974
5. Structural Models: An Introduction to the Theory of Directed Graphs;Harary,1965