Adjacency Matrices
Colin D. Walter · SIAM Journal on Algebraic and Discrete Methods · 1986
For a graph $\Gamma $ with vertex set V an algebra of adjacency matrices is defined and viewed as an equivalence relation on $V \times V$ with certain nice properties. This can be used in algorithms to find automorphisms of graphs and isomorphisms between graphs. It also provides intersection numbers independent of the labelling on V which determine the similarity class of the adjacency algebra.