Intersection numbers for coherent configurations and the spectrum of a graph.

Colin D. Walter Intersection numbers for coherent configurations and the spectrum of a graph. 201-204 1983 35 J. Comb. Theory, Ser. B 2 http://dx.doi.org/10.1016/0095-8956(83)90072-2 db/journals/jct/jctb35.html#Walter83