In graph theory, an edge regular graph is defined as follows. Let G = (V,E) be a regular graph with v vertices and degree k. G is said to be edge regular if there is also integer λ such that:
Every two adjacent vertices have λ common neighbors.
A graph of this kind is sometimes said to be an er(v,k,λ).
I want know about eigenvalues of edge regular graph, how can we find eigenvalue of this graph?